MC-NRLF 


075 


UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALLIDIC: 

1868^^^,  19O1 


THE  ENGINEERING  RECORD  SERIES 


STEAM  HEATING 

AND 

VENTILATION 


BY 


WILLIAM    S.    I^ONROE,  M.  E. 

Member  American  Society  of  Mechanical  Engineers. 
Member  American  Society  of  Heating  and  Ventilating  Engineers. 
Member  Western  Society  of  Engineers. 


NEW    YORK 

THE    ENGINEERING    RECORD 
1902 


<A 


HALLIDiE 


COPYRIGHT,  1902,  BY  THE  ENGINEERING  RECORD. 


Preface. 

The  chapters  comprising  this  book  were  originally  written  as  a 
•series  of  articles  for  The  Engineering  Record  and  have  been  some- 
what revised  for  their  present  form. 

It  has  been  the  aim  of  the  writer  to  present  briefly  the  theoreti- 
cal considerations  involved  in  the  design  of  heating  and  ventilating 
plants,  and  to  compile  the  best  of  the  large  array  of  empirical 
formulas  and  data  in  a  way  that  will  be  of  value  to  those  interested 
in  the  current  practice  of  the  art. 

The  writer  has  taken  the  liberty  to  refer  frequently  to  previous 
works  on  the  subject,  and  principally  to  those  of  Mills,  Baldwin 
and  Carpenter.  He  wishes  to  acknowledge  special  indebtedness 
to  Mr.  Alfred  E.  "Wolff  for  many  valuable  data. 

WM.  S.  MONROE. 

Chicago,  August,  1901. 


Table  of  Contents* 


Page 

Chapter  I. — Introductory  7 

Chapter  II.— Steam  Heating;  Systems  of  Piping  and  Steam  Supply..     13 

Chapter  III.— Steam  Heating  Apparatus 31 

Chapter  IV.— Indirect  Radiators 48 

Chapter  V. — Design  of  Radiation 60 

Chapter  VI.— Piping  and  Construction  Details 72 

Chapter  VII.— Mechanical  Ventilation— General  Principles 96 

Chapter  VIII.— Systems  of  Mechanical  Ventilation 103 

Chapter  IX.— Ventilating  Ducts 113 

Chapter  X.— Ventilating  Fans,  Heaters  and  Other  Apparatus 124 

Index  147 


STEAM    HEATING    AND    VENTILATION, 


CHAPTEE  L— INTRODUCTORY. 

The  first  really  practical  treatise  on  heating  and  ventilatioir 
seems  to  have  been  published  in  1824  by  Thomas  Tredgold,  and  in 
that  volume  much  space  is  given  to  the  importance  of  securing 
adequate  ventilation,  and  also  to  the  merits  of  heating  by  systems 
of  steam  pipes.  Mr.  Tredgold  gives  accounts  of  several  buildings 
which  were  successfully  heated  in  this  way.  It  is  cited  that  the 
first  factory  in  which  steam  was  used  for  heating  was  a  cotton  mill 
belonging  to  a  Mr.  Neil  Snodgrass,  in  which  a  steam  heating  sys- 
tem was  installed  in  1799.  This  was  doubtless  about  the  first  in- 
stance of  the  employment  of  steam  primarily  and  systematically 
for  the  purpose  of  heating.  Mr.  Tredgold  describes  a  factory 
which  was  equipped  with  a  steam-heating  system  in  1817  as  a  sub- 
stitute for  stoves,  which  had  been  previously  used.  The  building 
was  90  feet  by  30  feet,  exposed  on  all  sides,  and  four  floors  high. 
Each  floor  was  warmed  by  a  single  pipe  running  the  length  of  the 
building  at  the  ceiling  and  midway  between  the  sides.  The  sys- 
tem carried  30  pounds  steam  pressure,  but  besides  embodying  the 
most  inefficient  location  for  the  radiating  surface,  the  system,  as 
described,  did  not  have  over  450  square  feet  of  heating  surface  for 
a  building  containing  91,800  cubic  feet  of  space.  Mr.  Tredgold 
states  that  the  system  showed  great  improvement,  both  in  economy 
and  results,  over  the  previous  method,  adding  that  the  employees 
suffered  much  less  from  "chaps  and  chills,"  so  that  one  can  only 
imagine  the  wretched  condition  of  factory  employees  in  cold 
weather  previous  to  that  time,  even  in  the  comparatively  mild  cli- 
mate of  England. 

The  problem  of  artificial  ventilation  antedates  that  of  steam 
heating  by  more  than  half  a  century,  though,  of  course,  it  does 
not  antedate  the  heating  of  buildings  by  various  methods  more 
primitive.  Mr.  W.  F.  Butler,  in  a  handbook  on  ventilation,  pub- 


8  STEAM  HEATING  AND  VENTILATION. 

lished  some  years  ago,  states  that  the  first  scientific  consideration 
of  the  subject  of  artificial  ventilation  occurred  in  1723,  when  a 
certain  Dr.  Desaguliers  was  commissioned  to  institute  some  means 
for  making  the  atmosphere  in  the  House  of  Commons  more  habit- 
able ;  and  the  doctor  seems  to  have  installed  a  system  which  proved 
satisfactory,  although  it  had  been  previously  attempted  by  no  less 
a  personage  than  the  celebrated  architect,  Sir  Christopher  Wren. 
Since  that  time  the  question  of  ventilation  has  occupied  increasing 
attention  in  the  minds  of  physicians,  architects  and  other  scien- 
tific men  interested  in  the  public  welfare,  but  even  to  this  day 
what  may  be  called  "artificial"  or  forced  ventilation  remains  to 
a  large  extent  a  luxury. 

From  the  earliest  times  in  the  latitudes  of  northern  Europe  and 
North  America,  some  form  of  heating  in  cold  weather  has  been  a 
necessity  for  all  buildings,  whether  caves  or  palaces,  but  even  as 
late  as  the  latter  part  of  the  nineteenth  century  such  a  thing  as 
a  uniform  temperature  in  heated  rooms  in  severe  weather  was 
never  expected,  while  ventilation  was  invariably  secured  only  by 
such  means  as  would  be  accomplished  by  the  circulation  of  air 
through  doors  and  other  openings.  In  the  days  of  our  forefathers, 
when  houses  were  built  with  large  rooms  and  great,  high-ceiling 
halls,  and  when  people  spent  a  large  part  of  their  time  in  the  open, 
air,  there  was  in  reality  but  little  need  of  artificial  ventilation ;  and 
in  the  rude  homes  of  the  poorer  classes  that  which  was  secured 
through  poorly  constructed  walls  and  through  loose  windows  of 
oiled  paper  was  generally  much  more  than  was  desired.  With  the 
improvement  of  transportation  facilities,  however,  and  the  gath- 
ering of  large  numbers  of  people  into  small  areas,  and  compara- 
tively large  numbers  in  single  buildings,  the  need  of  artificial  ven- 
tilation, in  order  to  secure  anything  like  a  wholesome  atmosphere, 
gradually  became  apparent,  and  it  is  natural  that  the  demand  for 
such  ventilation  should  be  recognized  first  in  a  building  like  the 
House  of  Commons. 

Out  of  the  same  economic  conditions  arose  the  necessity  of  heat- 
ing buildings  by  steam.  Buildings  of  all  kinds  had  from  the  ear- 
liest days  been  heated  by  open  fireplaces,  in  which  logs,  and  later 
coal,  were  burned  in  considerable  quantities,  while  the  larger  pro- 
portion of  the  heat  escaped  up  the  flue.  But  forests  were  in  time 
reduced,  cities  grew,  and  buildings  were  made  larger  and  with  a 
much  larger  number  of  rooms;  and  people  were  forced  to  find 


STEAM  HEATING  AND  VENTILATION.  9 

more  economical  ways  of  heating  than  by  laboriously  carrying  ex- 
pensive fuel  to  separate  fires  in  each  individual  room.  Stoves  were 
built  to  get  more  uniform  combustion  and  save  some  of  the  heat 
lost  up  the  flue,  and  gradually  various  forms  of  distributing  heat 
through  many  rooms  from  one  central  fire  were  developed  TO 
economize  labor.  Heated  air,  heated  water  and  steam  were  all  in 
turn  experimented  with  as  a  means  of  distributing  heat,  anil  sys- 
tems employing  them  have  been  rapidly  and  scientifically  evolved 
to  meet  various  requirements,  and  are  to  this  day  very  widely 
used.  But  since  the  time  of  Tredgold,  heating  by  steam  has  in- 
creased in  extent  and  popularity  year  after  year,  especially  since 
the  increase  in  size  of  buildings  began  to  be  very  rapid,  and  its 
economy  of  operation  and  incidental  advantages  of  convenience 
and  simplicity  have  become  more  and  more  apparent,  until  at  the 
present  day,  in  some  form  or  another,  it  is  used  almost  universally 
in  all  installations  requiring  distribution  of  heat  over  any  consid- 
erable area.  In  this  country  it  is  well  within  the  memory  of  most 
men  in  active  life  when  even  our  largest  factories  and  office  build- 
ings were  heated  by  means  of  open  fires  and  stoves,  but  the  de- 
velopment from  a  primitive  life  to  a  congested  and  complex  civili- 
zation has  been  phenomenally  rapid,  especially  in  the  last  quarter 
century,  and  the  greatest  advances  in  steam  heating,  as  well  as 
in  most  practical  sciences,  have  been  made  in  that  period.  These 
have  chiefly  been  due  to  the  almost  universal  application  of  steam 
power  and  the  tremendous  economy  effected  by  the  use  of  exhaust 
steam  for  heating. 

The  problem  of  mechanical  ventilation,  therefore,  though  grow- 
ing out  of  much  the  same  economic  conditions,  was  solved,  to  a 
large  extent,  independently  of  the  question  of  heating;  and  with 
the  development  of  heat  distribution  by  steam  much  was  lost  in 
the  way  of  ventilation.  The  old-time  fireplace  and  stove  insured 
a  certain  amount  of  ventilation,  to  say  nothing  of  the  mental  ex- 
hilaration of  the  former,  but  heating  by  steam  was  accomplished 
with  no  ventilation  whatsoever.  Hygienically,  therefore,  it  was  a 
step  in  the  wrong  direction,  but  economically  the  lack  of  ventila- 
tion made  it  more  advantageous,  as  ventilation  requires  the  heat- 
ing of  all  incoming  air.  Heat  in  cold  weather  was  the  prime  es- 
sential, and  it  was  always  possible  to  obtain  some  amount  of  ven- 
tilation by  what  might  be  called  the  "natural  circulation"  of  air 
through  doors  and  windows.  The  fallacy  of  resorting  to  such 


10  STEAM  HEATING  AND  VENTILATION. 

methods  exclusively  has  been  pointed  out  in  many  tracts  and 
treatises  published  since  the  latter  part  of  the  eighteenth  century, 
but  the  fact  remains  that  even  to  the  present  day  a  vast  majority 
of  our  buildings,  a  large  proportion  even  of  our  factories,  churches 
and  schoolhouses,  and  most  of  our  fine  office  buildings,  with  their 
boasted  modern  improvements,  have  no  mechanical  means  for  in- 
suring an  adequate  ventilation. 

At  the  present  day  we  have  arrived  at  a  considerable  degree  of 
advancement,  however,  and  buildings  might  now  be  divided  into 
two  quite  distinct  classes — those  which  are  "densely  peopled"  and 
those  which  are  "sparsely  peopled" — and  our  advancement  is  such 
that  mechanical  ventilation  is  generally  looked  upon  as  a  necessity 
for  all  buildings  of  the  former  class,  which  may  include  school- 
houses,  churches,  hospitals,  theaters,  and  other  audience  halls. 
In  buildings  of  the  second  class,  such  as  residences,  office  build- 
ings and  hotels,  we  have  been,  as  a  rule,  satisfied  with  sufficient 
heat,  and  have  relied  upon  such  ventilation  as  is  secured  by  the 
natural  circulation  methods.  In  such  buildings,  therefore,  the 
system  of  heating  most  used  is  that  known  as  "direct  radiation," 
in  which  radiators,  or  some  form  of  radiating  surface,  are  located 
in  each  room,  and  connected  by  an  arrangement  of  piping  to  a  cen- 
tral source  of  steam  or  hot-water  supply.  The  rooms  are  heated 
by  radiation  from  the  hot  surface  and  by  contact  of  the  air  with 
it,  but  no  provision  is  made  for  the  supply  of  fresh  air. 

Several  adaptations  of  the  ordinary  direct-radiation  system  of 
steam  heating  have  been  developed,  however,  with  a  view  of  ob- 
taining the  advantage  of  ventilation  which  was  secured  in  the  old- 
time  stoves  and  fireplaces.  The  principal  one  of  these  is  what  i* 
known  as  the  system  of  "indirect  radiation,"  in  which  the  radia- 
tors, instead  of  being  located  in  the  rooms  to  be  heated,  are  all 
placed  below  them,  generally  in  the  basement  of  the  building,  and 
are  enclosed  in  boxes,  which  are  provided  with  air  inlets  from  the 
outside  of  the  building,  and  with  flues  running  to  the  room  to  be 
heated.  Fresh  air  coming  through  the  inlet  in  contact  with  the 
radiator  is  heated  and  rises  through  the  vertical  flue  by  the  natu- 
ral upward  tendency  of  hot  air.  Both  heat  and  ventilation  are  in 
this  way  provided  to  the  rooms  by  the  incoming  hot  air.  This  sys- 
tem has  been  much  used  in  residences,  and  also  to  a  small  extent 
in  some  buildings  of  the  "densely-peopled"  class,  such  as  hos- 
pitals and  hotels.  But  the  system  has  a  decided  disadvantage,  due 


STEAM  HEATING  AND  VENTILATION.  11 

to  the  fact  that  the  amount  of  ventilation  secured  is  practically 
proportional  to  the  amount  of  heat  required,  and  in  warm  weather 
but  little,  if  any,  ventilation  is  obtained.  Furthermore,  experience 
shows  that  in  order  to  ensure  reliability  it  is  necessary  to  have  a 
separate  flue  for  almost  every  room  and  to  locate  the  radiators, 
directly  beneath  the  vertical  flue,  so  that  in  buildings  of  any  size,, 
especially  those  more  than  one  or  two  stories  in  height,  the  ar- 
rangement of  radiators  in  the  basement  becomes  difficult,  and  the 
system  of  air  flues,  which  are  necessarily  large,  is  complex  and  ex- 
pensive in  space  and  also  in  construction. 

In  order  to  avoid  the  difficulties  of  the  system  of  "indirect  radia- 
tion" and  yet  secure  some  ventilation,  a  combination  has  been  de- 
veloped which  goes  under  the  significant  title  of  "direct-indirect 
radiation."  In  this  the  radiators  are  located  in  each  separate  room,, 
but  they  are  of  special  construction,  and  provided  with  air  connec- 
tions through  the  walls  of  the  building  so  arranged  that  a  certain 
amount  of  air  can  be  admitted  through  this  connection  so  as  to 
pass  around  the  radiator,  becoming  heated  by  contact  with  it.  The 
room  is  therefore  heated  both  by  direct  radiation  and  by  the  in- 
coming current  of  fresh  hot  air,  and  considerable  ventilation  is- 
secured. 

In  this  system,  as  in  the  "indirect,"  ventilation  in  warm  weather 
is  dependent  on  open  windows  and  doors,  and  it  has  been  as  yet 
but  little  used.  It  has,  however,  in  a  few  cases  been  adapted  to 
office  buildings  and  hotels,  and  in  the  opinion  of  the  writer  we 
may  look  for  a  very  decided  development  of  the  "direct-indirect'* 
during  the  immediate  future  in  buildings  of  the  more  sparsely- 
peopled  character,  where  the  amount  of  ventilation  required  per 
square  foot  of  floor  area  is  comparatively  small.  But  for  such 
buildings  this  system  only  achieves  its  best  results  when  combined 
with  a  mechanical  system  for  exhausting  the  air. 

As  already  mentioned,  we  have,  perhaps,  arrived  to-day  at  a 
point  in  the  advancement  of  hygienic  science  where  some  system 
of  artificial  or  mechanical  ventilation  is  looked  upon  as  necessary 
for  all  buildings  of  what  the  author  has  called  the  densely-peopled 
class.  It  is  difficult  to  define  the  limits  of  such  buildings,  as  the 
height  and  nature  of  the  room  and  length  of  time  occupied  affect 
the  question,  but  in  a  general  way  any  room  or  apartment  in  which 
each  individual  occupies  less  than  40  square  feet  of  floor  area 
should  be  included  in  such  a  classification,  especially  if  occupied 


12  STEAM  HEATING  A\D  VENTILATION. 

more  than  two  or  three  hours  at  a  time.  The  systems  which  may 
be  employed  for  mechanical  ventilation  are  numerous  and  varied, 
"but  they  all  embody  the  use  of  fans  of  one  kind  or  another  for 
forcing.the  air  into  the  rooms,  or  exhausting  it,  or  both,  with  prop- 
er provision  for  heating  the  incoming  air  in  cold  weather,  and  some 
one  of  the  three  heating  systems  is  frequently,  if  not  generally, 
employed  in  connection  with  a  system  of  mechanical  ventilation. 


CHAPTER  II.— STEAM  HEATING;  SYSTEMS  OF  PIPING 
AND  STEAM  SUPPLY. 

Systems  of  piping. — The  three  systems  of  steam  heating  as  de- 
scribed in  Chapter  I. — the  direct,  indirect  and  direct-indirect 
radiation — are  governed  by  much  the  same-  rules-  in  the  matter  of 
piping  arrangement  and  steam  supply,  the  two  latter  requiring 
only  special  rules  for  proportioning  the  amount  of  heating  sur- 
face and  for  the  arrangement  of  air  supply-.  As-  regards  piping, 
there  are  the  one-pipe  and  two-pipe  systems,  with  several  varieties 
and  combinations  of  each;  and  as  regards  the  steam  supply,  there 
are  high  and  low-pressure  systems,  exhaust  systems,  gravity  sys- 
tems, vacuum  systems — terms  more  or  less  indefinite  and  somewhat 
mixed  in  their  application. 

The  essential  requisites  of  a  steam-heating  system  comprise: 
First,  a  source  of  steam  supply,  which  may  be  either  an  independ- 
ent boiler  or  a  heater  or  tank  of  some  description  supplied  with 
exhaust  steam  from  an  engine.  Second,  a  system  of  piping  to 
conduct  the  steam  from  the  .source  of  supply  to  the  radiators. 
Third,  a  series  of  radiators  or  radiating  surfaces  consisting  of  en- 
closed spaces  in  which  the  steam  is  condensed  by  the  cooler  air 
of  the  room  on  the  outside  of  the  surface.  Fourth,  a  system  of 
return  pipes  through  which  the  water  condensed  in  the  radiators 
is  removed;  and  fifth,  a  receptacle  into  which  this  water  is  drained. 

The  second  and  fourth  of  these  requisites  may  be  either  wholly 
or  in  part  embodied  in  one,  as  may  also  the  first  and  fifth.  It  might 
be  more  briefly  stated,  therefore,  that  the  prime  requisites  are 
only  the  source  of  steam  supply,  the  radiating  surface  and  a  sys-i 
tern  of  piping  connecting  them.  .  But  even  though  the  supply  and 
the  return  pipes  be  embodied  in  the  same  system,  it  is  just  as 
necessary  that  they  be  so  arranged  as  to  dispose  of  the  water  of 
condensation  as  it  is  for  them  to  supply  steam  to  the  radiator, 
which  fact  should  never  be  lost  sight  of. 

One-pipe  system. — The  simplest  possible  heating  system,  there^ 
fore,  is  one  which  would  be  known  as  .a  one-pipe  gravity  system, 


14 


STEAM  HEATING  AND  VENTILATION. 


such  as  is  indicated  in  Figure  1.  The  steam  is  generated  in  the 
boiler,  flows  through  the  pipes  to  the  radiators,  the  water  condensa- 
tion as  it  is  formed  in  the  radiators  draining  out  along  the  bottom 
of  the  pipes  and  back  to  the  boiler  by  gravity,  to  be  re-evaporated 
into  steam.  Such  a  system  as  this  could  be  applied  only  to  a  very 
small  plant,  and  one  in  which  the  pipes  could  be  made  comparative- 


Figure  1.— The  One-pipe  System. 


JO, 

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a 

5^o/n  Wa/>f. 

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rDraln. 

J 

>W»r  f  tvet 

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in  ttoilv. 

Figure  2.— The  Two-pipe  System. 


ly  of  large  size  and  given  a  very  decided  fall  toward  the  boiler  from 
all  directions. 

Two-pipe  system. — The  more  usual  system  of  piping,  and  that 
first  employed,  is  known  as  the  "two-pipe  system,"  and  is  repre- 
sented in  Figure  2.  In  this,  each  radiator  has  one  pipe  for  supply- 
ing steam  and  another  to  remove  the  water  of  condensation.  The 
only  object  in  the  two-pipe  connection  is  to  provide  a  freer  and 
more  positive  flow  of  steam  and  condensed  water,  but  this  is  a 


STEAM  HEATING  AND  VENTILATION.  15 

very  important  consideration.  In  a  one-pipe  system,  such  as  indi- 
cated by  Figure  1,  the  water  of  condensation  flows  from  the  radia- 
tors back  to  the  boilers  against  the  current  of  steam,  falling 
through  the  steam  in  the  vertical  pipes  and  flowing  along  the  bot- 
tom of  the  horizontal  pipes.  Such  a  simple  system  as  this,  shown 
in  Figure  1,  might  be  employed,  and  to  a  considerable  extent,  if 
the  pipes  are  of  ample  size,  and  also  if  there  are  no  valves  on  the 
radiators,  so  that  steam  can  be  turned  on  the  entire  system  at 
all  times.  In  this  case  there  would  be  a  constant  and  practically 
uniform  flow  of  water  through  the  pipes,  and,  if  these  were  prop- 
erly laid  out,  the  system  might  give  perfect  satisfaction.  But  it  is 
impracticable  to  have  all  the  radiators  of  a  system  turned  on  at 
one  time,  and  the  difficulty  with  such  a  system  is  made  evident 
the  minute  steam  is  turned  into  a  cold  radiator.  When  the  steam 
comes  in  contact  with  a  perfectly  cold  radiator  a  large  amount  is 
condensed  at  once  in  heating  the  cold  iron,  and  as  soon  as  the 
pressure  becomes  adjusted  this  bulk  of  water  flows  out  of  the  radia- 
tor connection  at  one  time  and  drops  down  the  vertical  pipe.  When 
it  reaches  the  horizontal  main  in  the  basement  it  is  picked  up  by 
the  current  of  steam  and  carried  to  other  parts  of  the  system, 
filling  up  the  pipes  in  places;  and  as  it  is  relatively  much  colder 
than  the  steam,  the  latter,  in  trying  to  get  by  it,  is  suddenly  con- 
densed, disturbing  the  equilibrium  of  pressure,  as  we  might  say, 
and  producing  the  disagreeable  crackling  and  pounding  noises 
which  are  always  encountered  in  poorly  constructed  heating  sys- 
tems, and  which  are  commonly  known  undei  the  name  of  water- 
hammer.  This  noise,  besides  being  very  annoying  to  the  occupants 
of  the  building,  interferes  with  the  circulation  of  steam  and  also 
produces  undue  strains  in  the  piping. 

The  two-pipe  system  to  a  certain  extent  does  away  with  these 
difficulties ;  that  is,  in  using  the  two-pipe  connectioL  it  is  generally 
easier  to  avoid  the  water-hammer  and  other  annoyances  incident  to 
imperfect  circulation;  but  unless  the  pipes  are  properly  propor- 
tioned and  properly  drained  the  sarrnj  difficulties  will  be  encoun- 
tered. The  simple  one-pipe  system,  indicated  in  Figure  1,  is  there- 
fore, as  before  stated,  rarely,  if  ever,  used,  but  there  are  a  number 
of  modifications  of  it  which  are  used  with  decided  success,  and  in 
some  of  the  largest  installations. 

One-pipe  system  with  separate  return  main. — The  simplest  one- 
pipe  system  usually  employed  is  represented  in  Figure  3.  In  this 


16 


STEAM  HEATING  AND  VENTILATION. 


the  horizontal  steam  main  in  the  basement  is  pitched  so  as  to  drain 
away  from  the  boiler,  and  at  its  extreme  end  a  return  pipe  is  con- 
nected and  led  back  to  the  boiler,  entering  it  below  the  water-line. 
In  this  way  the  flow  of  steam  and  water  of  condensation  is  in  the 
same  direction  in  the  mains,  and  upon  the  sudden  condensation  of 
considerable  steam,  as  will  occur  when  turning  steam  into  a  cold 
radiator,  the  water  falls  down  the  risers  against  the  current  of 
steam;  but  in  the  main  it  is  propelled  along  in  the  same  direction 
as  the  steam  current.  If  the  mains  are  extensive  they  can,  more- 
over, be  drained  at  several  different  points.  This  system  is  exten- 
sively used  for  residences  and  buildings  of  only  a  few  stories  in 
height,  and  it  has  also  been  used  in  larger  installations.  The  Chi- 
cago Athletic  Club,  a  building  ten  stories  in  height,  is  heated  by 


O .Oar. 


Figure  3. — A  Common  Type  of  One-pipe  System. 


exhaust  steam  with  this  system  of  piping  with  a  pressure  of  not 
over  2  pounds  in  the  coldest  weather,  and  with  little,  if  any> 
difficulty  with  water-hammer.  In  such  a  plant  the  risers  as  well 
as  the  mains  must  be  of  ample  size,  and  the  latter  must  have  suffi- 
cient pitch  and  be  thoroughly  drained.  The  consideration  of  these 
questions  as  affecting  the  size  of  the  pipes  will  be  taken  up  in  a 
subsequent  chapter. 

Mills'  system. — The  only  system  of  single-pipe  connection  which 
has  been  very  extensively  .used  in  high  buildings,  such  as  the  mod- 
ern office  building,  is  that  known  as  the  one-pipe  overhead,  or 
Mills'  system,  and  is  indicated  diagrammatically  in  Figure  4.  In 
this  system  the  steam  is  conducted  through  a  large  main  supply 
pipe  to  the  attic  of  the  building,  or  to  the  ceiling  of  the  top  floor. 


STEAM  HEATING  AND  VENTILATION. 


17 


and  from  this  the  mains  extend  around  the  building  to  supply  the 
risers.  The  risers  are  connected  to  the  return  mains  in  the  base- 
ment. It  will  be  seen  that  in  this  system  the  current  of  steam 
and  water  of  condensation  is  everywhere  in  the  same  direction  ex- 
cept in  the  connections  to  the  radiators,  and  the  risers  should  be 
sufficient  in  number  so  that  these  connections  may  be  compara- 
tively short.  This  arrangement  has  the  very  decided  advantage 
over  the  ordinary  upward-supply  one-pipe  system  that  the  water 
of  condensation  that  falls  down  the  risers  from  the  radiators  does 
not,  when  it  reaches  the  horizontal  pipe  at  the  bottom,  encounter 
the  main  current  of  steam,  as  the  horizontal  pipe  is  only  a  drain 
pipe,  in  which  there  is  practically  no  steam  current,  and  which  is 
designed  solely  to  dispose  of  this  water. 


a 

a 

a 

cr 

cr 

Floor. 

£L//.«r 
SL^w* 

Q    noon 

a 

a 

a 

a 

a 

^n     ^ 

-a 

cr 

« 

a 

*  | 

cr 

a 

a 

OLflto: 
_Jasemenr. 

a 

a  .    .. 

ffeturri. 

3H 

r 

Rttvrn. 

~f 

C-  —  -—  — 

Figure  4.— The  Mills  System. 


Two-pipe,  overhead  system. — The  principle  of  the  two-pipe  system 
is  much  the  same  in  all  cases,  but  special  adaptations  of  it  are  made 
to  meet  special  conditions.  There  is,  for  example,  a  two-pipe  over- 
head system  in  which  steam  mains  are  in  the  attic  as  well  as  in  the 
one-pipe  overhead,  but  there  is  a  separate  set  of  return  risers 
which  connect  with  the  return  mains  in  the  basement.  But  each 
supply  riser  should  also  be  drained  into  the  basement  returns.  The 
arrangement  has  been  but  very  little  used. 

Drainage  of  pipes. — It  must  be  remembered  that  in  any  system 


18  STEAM  HEATING  AND  VENTILATION. 

there  is  always  a  certain  amount  of  water  in  the  supply  mains  and 
risers  due  to  the  radiation  from  the  pipes  themselves.  If  the 
pipes  are  thoroughly  covered  with  a  good  non-conductor  of  heat 
there  is  but  very  little  water  from  this  cause ;  but  little  as  it  is,  the 
mains  must  be  so  run  that  it  will  flow  to  certain  points,  where  it 
must  be  drained  into  the  return  or  into  proper  receptacles.  If  the 
steam  pipes  are  arranged  so  that  water  can  accumulate  at  any 
point,  trouble  is  sure  to  follow.  It  is  a  fundamental  principle  in 
steam  heating  that  pipes  shall  be  so  graded  that  water  of  conden- 
sation will  tend,  by  the  action  of  gravity,  to  flow  with  the  current 
of  steam  to  certain  points,  where  it  can  be  properly  drained  off. 

The  various  systems  of  piping  are  sometimes  more  or  less  com- 
bined in  the  same  installation,  and  when  radiators  are  of  very  large 
size  they  should,  if  possible,  be  given  both  a  supply  and  return  con- 
nection, as  the  principal  advantage  of  the  double  connection  lies 
in  the  internal  circulation  which  tends  toward  the  more  rapid 
removal  of  air  and  water.  More  will  be  said  on  the  subject  of 
radiator  connections  in  a  subsequent  chapter  on  radiators. 

Gravity  systems. — In  the  preceding  discussion  and  the  accom- 
panying diagrams  we  have  assumed  that  the  water  of  condensation 
returns  through  the  return  pipes  directly  to  the  boiler,  there  to 
be  re-evaporated  into  steam  by  the  fire  on  the  grate.  This  is 
what  is  known  as  the  "gravity  system"  of  steam  supply,  and  is 
self-regulating  as  to  water  consumption,  except  for  such  small 
amounts  of  steam  and  water  as  may  be  lost  by  leaks.  It  is  but  one 
of  the  many  methods  of  steam  supply,  though  the  one  now  most 
employed  where  the  plant  is  used  only  for  heating  and  there  is 
no  steam  power. 

In  the  gravity  system  the  water  stands  in  the  return  pipes  and 
risers  at  practically  the  same  level  as  that  in  the  boiler,  though  in 
the  remote  parts  of  the  system  it  rises  above  the  boiler  level  by  a 
height  equivalent  to  the  pressure  required  to  effect  the  circula- 
tion through  the  system.  For  this  reason  gravity  systems  should 
l>e  designed  for  free  circulation,  with  pipes  of  ample  size,  the  dif- 
ference of  pressure  required  between  the  steam  mains  and  the 
most  extreme  point  of  the  returns  never  exceeding  a  pound  or  two 
per  square  inch.  Gravity  systems  are  therefore  generally  run  at 
very  low  pressures,  though  frequently  in  very  cold  weather  as  much 
as  15  pounds  is  carried  for  the  sake  of  the  higher  temperature  of 
steam.  The  operation  of  this  system  is  the  same  at  any  pressure. 


STEAM  HEATING  AND  VENTILATION.  19 

The  gravity  system  is  a  comparatively  recent  development,  the 
earliest  steam-heating  systems  being  generally  auxiliary  to  a  steam- 
power  plant.  In  these  the  steam  was  taken  direct  from  the  boiler 
supplying  the  engine,  and  the  return  water  was  run  through  a 
steam  trap  into  an  open  tank,  from  which  the  water  supply  was 
taken  for  the  boilers.  This  method  is  still  employed  in  many 
old  plants. 

Exhaust  steam  heating. — The  greater  economy  in  high-pressure 
steam  for  engines,  however,  gradually  increased  the  boiler  pressure 
used  for  steam  power,  and  with  this  increase  in  pressure  it  be- 
came difficult  to  heat  a  building  directly  from  the  same  boiler 
that  supplied  steam  to  the  engines,  as  steam  heating  at  high  press^ 
ure  was  found  unsatisfactory  for  many  reasons,  principally  on  ac- 
count of  the  very  high  temperature  of  the  radiators  and  the  lia- 
bility to  leaks  and  the  increased  danger  from  water-hammer.  And 
furthermore,  the  same  desire  for  greater  economy  which  had  in- 
creased engine  pressures  drew  the  attention  of  steam  users  to 
the  value  of  the  latent  heat  in  exhaust  steam  for  heating  purposes. 

A  brief  study  of  the  steam  engine  shows  us  that  not  much  over 
12  per  cent,  of  the  heat  energy  supplied  to  an  engine  is  transformed 
into  mechanical  work,  and  by  far  the  major  part  of  the  wasted  heat 
•escapes  in  the  latent  heat  of  the  exhaust  steam.  This  heat,  though 
it  has  been  thus  far  impossible  to  transform  it  into  mechanical 
energy,  is  readily  available  for  heating  purposes;  but  a  generation 
ago,  when  it  was  first  proposed  to  use  exhaust  steam  for  heating, 
the  problem  involved  the  then  serious  question  of  back  pressure 
on  the  engines.  Heating  systems  at  that  time  were  built  to  ac- 
commodate the  high  pressure  then  in  use  and  with  what  would 
now  be  called  very  small  pipes,  and  admitting  exhaust  steam  into 
such  a  system  required  a  considerable  pressure  on  the  exhaust  side 
of  the  engine  to  force  steam  through  the  piping  and  radiators  and 
the  water  of  condensation  out  through  the  returns. 

The  back  pressure  necessary  frequently  amounted  to  10  or  15 
pounds  per  square  inch,  and  certainly  made  a  decided  reduc- 
tion in  the  economy  of  the  engine.  It  at  once  became  a  question 
whether  the  saving  by  using  exhaust  steam  exceeded  the  loss  on 
account  of  the  back  pressure  on  the  engine.  If  the  back  pressure 
was  very  high  in  comparison  to  the  mean  pressure  in  the  engine 
cylinder  there  might  be  difficulties  in  the  practical  operation  of 
the  engine ;  but  as  far  as  the  theoretical  consideration  of  the  coal 


20  STEAM  HEATING  AND  VENTILATION. 

pile  goes,  it  is  more  economical  to  use  exhaust  steam  even  at  a 
high  back  pressure. 

As  heating  systems  are  now  designed,  one  which  requires  a 
pressure  of  5  pounds  to  ensure  a  good  circulation  is  defective  in 
design,  and  2  pounds  is  more  than  ought  to  be  required  in  most 
cases.  A  back  pressure  of  this  amount  on  an  engine  running  at 
50  pounds  mean  effective  pressure  would  increase  the  coal  con- 
sumption but  a  fraction  of  1  per  cent.,  while  taking  the  heating 
power  that  is  available  in  the  exhaust  steam  directly  from  the 
boiler  would  increase  the  coal  consumption  over  60  per  cent. 

Another  consideration  enters,  however,  into  the  question  of  cir- 
culation in  a  steam-heating  apparatus.  Besides  merely  forcing  the 
steam  and  water  through  the  radiators  and  piping,  it  is  necessary 
to  force  out  the  air  which  accumulates,  and  to  do  this  the  S3rstem 
must  carry  a  pressure  somewhat  above  that  of  the  atmosphere, 
unless  a  vacuum  system,  which  will  be  described  later,  be  used. 

Theoretically  it  would  be  possible  to  operate  a  simple  gravity 
system  below  the  atmospheric  pressure  if  the  whole  system  was  per- 
fectly air  tight  and  the  air  was  all  boiled  out  of  the  water  and 
forced  out  of  the  system  in  the  first  place.  In  such  a  case  if  the 
fires  were  put  out  and  the  system  allowed  to  become  cold,  the  con- 
densation of  steam  would  leave  a  perfect  vacuum,  and  on  starting 
up  the  fire,  steam  could  be  carried  at  any  pressure  below  or  above 
the  atmospheric,  according  to  the  intensity  of  the  fire. 

But  if  it  be  attempted  to  run  much  below  atmospheric  pressure 
the  slightest  leak  anywhere  in  the  system  will  rapidly  break  the 
vacuum  and  allow  air  to  accumulate.  It  is,  however,  impossible 
to  make  a  system  theoretically  air  tight,  and  steam  invariably 
contains  some  air  from  the  feed  water,  as  water  will  absorb  sev- 
eral times  its  own  volume.  Air  in  the  radiators  and  piping  is, 
therefore,  an  evil  that  cannot  be  avoided,  and  it  rapidly  accumu- 
lates in  the  radiators  or  ends  of  pipes  where  the  flow  of  steam  is 
slowest.  Consequently  an  air  valve  is-  almost  a 'necessity  on  every 
radiator,  and  those  which  are  now  almost  universally  used  are  au- 
tomatic ;  that  is,  they  close  as  soon  as  the  hot  steam  comes  in  con- 
tact with  them,  and  open  if  air  accumulates  and  they  become  cold. 
To  some  extent  these  automatic  air  valves  enhance  the  air  prob- 
lem, inasmuch  as  when  the  radiator  is  cold  it  entirely  fills  with  air 
at  atmospheric  pressure.  In  any  case  the  result  of  the  presence  of 
air  is  that  the  pressure  of  steam  in  the  system  must  be  sufficient 


STEAM  HEATING  AND  VENTILATION. 


21 


to  force  the  air  out,  though  for  this  purpose  a  fraction  of  a  pound 
above  the  atmospheric  should  suffice;  and  frequently  better  re- 
sults are  obtained  with  such  a  slight  excess  than  with  a  greater 
pressure.  A  subsequent  chapter  on  radiators  will  discuss  the  action 
of  air  and  position  of  an  air  valve. 

Arrangement  of  exhaust  heating  systems. — This  brings  us  to  a 
discussion  of  the  methods  by  which  low-pressure  exhaust  steam  is 
employed  for  heating.  The  simplest  method,  and  the  one  usually 
employed  in  exhaust-steam  heating,  consists  in  dividing  the  main 
exhaust  pipe,  which  receives  the  exhaust  steam  from  all  engines 
and  pumps  about  the  steam  plant,  into  two  branches,  one  leading 
to  the  atmosphere,  the  other  being  connected  to  the  heating  sys- 
tem. On  the  pipe  to  the  atmosphere  is  placed  a  back-pressure 
valve,  the  object  of  which  is  to  automatically  maintain  a  uniform 
pressure  upon  the  exhaust  and  upon  the  heating  system,  so  that 


FiG.SA  Fio.SB 

Forms  of  Back-Pressure  Valve. 

the  steam  may  flow  into  the  heating  system  as  fast  as  it  condenses 
in  the  radiators.  Two  forms  of  back-pressure  valves  are  shown  in 
Figure  5,  A  and  B,  the  essential  feature  consisting  of  a  disk  that  is 
weighted  so  that  when  the  pressure  on  the  inlet  side  exceeds  a 
certain  amount  the  disk  rises  and  allows  sufficient  steam  to  escape 
to  the  atmosphere.  The  water  formed  by  the  condensation  of 
steam  in  the  heating  system  is  carried  back  through  the  main 
return  pipe  to  some  kind  of  receiver,  and  is  pumped  into  the  boil- 
ers. It  is  generally  arranged  to  pass  through  some  kind  of  an 


22  STEAM  HEATING  AND  VENTILATION. 

exhaust-steam  feed-water  heater  on  its  way  to  the  boiler.  The 
pump  is  also  usually  operated  automatically,  as  will  be  discussed 
later. 

The  feed-water  heater  is  an  essential  in  all  steam  plants,  and  its 
purpose  is  to  utilize  as  much  as  possible  of  the  heat  in  the  exhaust 
steam  in  heating  the  water  fed  to  the  boiler.  As,  however,  not 
more  than  18J  per  cent,  of  the  exhaust  steam  can  in  any  case  be 
required  to  heat  the  coldest  feed  water  to  the  full  temperature  of 
the  exhaust  steam,  212  degrees  Fahr.,  there  is  always  a  con- 
siderable quantity  left,  which  can  be  utilized  in  heating  the  build- 
ing; and  furthermore,  as  the  hot  return  water  is  always  in  one 
way  or  another  fed  back  to  the  boiler,  the  more  steam  that  is  re- 
quired for  the  building  the  more  return  water  there  is  and  the  less 
steam  is  needed  to  heat  cold  feed  water.  If  the  heat  in  the  exhaust 
steam  is  not  thus  used  in  heating  the  feed  water  or  heating  the 
building,  or  both,  it  would  be  wasted,  and  its  equivalent  in  coal 
would  have  to  be  used  under  the  boiler  to  replace  it. 

There  are  two  distinct  classes  of  exhaust-steam  feed-water  heat- 
ers; the  closed  or  pressure  heaters,  and  the  open  heaters.  In  the 
former  the  feed  water  is  pumped  through  the  heater  against  the 
boiler  pressure;  the  exhaust  steam  passing  into  an  inlet  chamber,, 
and  generally  through  a  series  of  tubes  into  the  outlet  chamber,, 
the  tubes  being  set  in  wrought-iron  plates,  which  divide  the  inlet 
and  outlet  chambers  from  the  water  space  around  the  outside  of 
the  tubes.  In  a  water-tube  heater  the  position  of  the  steam  and 
water  is  reversed.  In  the  open  heater  the  water  and  steam  are 
practically  together  in  the  same  chamber,  the  water  flowing  in 
from  some  source  against  only  the  pressure  of  the  exhaust  steam. 
The  suction  of  the  feed  pump  is  connected  to  the  heater  and  the 
delivery  direct  to  the  boilers.  With  the  closed  heater  cold  water 
is  pumped  through  the  heater  to  the  boiler,  while  with  the  open 
heater  hot  watei  from  the  heater  is  pumped  direct  to  the  boiler. 

The  scheme  of  steam  supply  described  is  represented  in  Figure 
6,  and  is,  with  various  modifications  of  detail,  almost  universally 
employed  in  heating  systems  in  which  exhaust  steam  is  used.  It 
will  be  noticed  that  in  the  figure  the  pipe  to  the  heating  system  is 
provided  with  a  live-steam  connection.  This  is  necessary  in  a 
great  many  plants  where,  in  extremely  cold  weather,  the  exhaust 
steam  is  not  sufficient  to  heat  the  building.  In  modern  practice 
such  a  connection  is  always  provided  with  a  reducing-pressure 


STEAM  HEATING  AND  VENTILATION.  23 

valve.  These  valves,  one  of  which  is  represented  by  Figure  5  C, 
are  of  such  construction  that  they  can  be  set  for  any  desired  differ- 
ence between  the  highland  low-pressure  sides.  The  reducing  valve 
must  always  be  set  for  a  pressure  somewhat 
lower  than  that  at  which  the  back-pressure 
valve  opens,  as  otherwise  some  live  steam  from 
the  reducing  valve  might  pass  through  the 
back-pressure  valve  to  the  atmosphere  and  thus 
be  wasted. 

Figure  7  shows  an  arrangement  with  a  press- 
ure heater  which  is  much  employed  in  steam- 
heating  systems.  The  exhaust  steam  enters 
the  bottom  of  the  heater  and  goes  out  at  the 
top.  The  connection  is  also  provided  with  a 
by-pass  so  arranged  that  in  case  it  is  necessary 
to  shut  out  the  heater  for  repairs  or  cleaning,, 
the  valve  B  in  the  by-pass  may  be  opened  and 
the  valves  A  and  C  closed,  so  that  the  steam  will  pass  around 
the  heater.  In  ordinary  use  the  valve  B  in  the  by-pass  is  closed 
and  A  and  C  opened.  The  arrangement  of  the  supply  to  the  heat- 
ing system,  which  is  connected  to  the  outlet  of  the  heater,  and. 


*  -Free  Exhaust, 
y  Back-Pressure  Valve. 


Figure  6 — Exhaust  Steam-Heating  Supply  Connections. 

the  back-pressure  valve  on  the  free  exhaust,  is  the  same  as  indi- 
cated in  Figure  6.  The  main  return  pipe  is  run  into  a  cylindrical 
receiving  tank,  from  which  the  water  is  pumped  through  the 
heater.  Attached, to  the  receiving  tank  is  an  automatic  pump 
governor,  which,  by  means  of  a  float  operating  on  the  steam  sup- 


/& 

/ir  -.« 

I   UNIVERSITY  , 


24 


STEAM  HEATING  AND  VENTILATION. 


ply  to  the  pump,  regulates  the  level  of  water  in  the  receiving  tank. 
As  soon  as  the  water  in  the  tank  rises  above  the  proper  level  the 
pump  is  started  by  the  float,  and  when  it  falls  below  this  level 
the  pump  is  stopped. 

Figure  8  represents  an  arrangement  with  an  open  heater.  The 
steam  connection  is  precisely  similar  in  principle,  but  a  different 
arrangement  of  details  is  indicated,  the  valves  being  lettered  to 
correspond  with  those  in  Figure  7.  The  returns  are  run  into  a 
receiving  tank  similar  to  the  other  arrangement,  but  this  tank 


t  free  Exhaust  to  Open  Air. 
Back-  Pressure  Valve. 


Main  Supply  to  Heating  System. 


Water  Level  in  Returns. 
I  \  Main  Return 

Glass.  {Receiving 


Figure  7— Arrangement  with  Pressure  Heater. 

is  connected  directly  to  the  heater,  and  practically  forms  a  part 
of  it.  The  automatic  float  which  controls  the  operation  of  the 
pump  is  generally,  in  such  cases,  connected  directly  on  to  the  heat- 
er, as  indicated  in  the  governor  marked  D. 

In  Figure  8,  on  the  left  of  the  heater,  is  indicated  another  float 
governor,  E,  which  is  frequently  attached  to  heaters  of  this  charac- 
ter. This  operates  on  the  cold-water  supply.  In  this  connection 
it  will  be  noted  that  frequently  in  moderate  weather  only  a  portion 
of  the  exhaust  steam  is  needed  to  heat  the  building,  the  remainder 
escaping  through  the  back-pressure  valve.  In  such  cases  it  is  neces- 
sary to  make  up  the  loss  of  water  by  taking  a  certain  amount  from 
the  city  mains  or  other  source  of  supply.  With  the  open  type  of 


STEAM  HEATING  AND  VENTILATION. 


25 


heater  this  is  generally  run  directly  into  the  heater  and  sprayed 
through  the  current  of  exhaust  steam.  It  is  for  the  control  of 
this  cold-water  supply  that  the  governor,  E,  is  provided.  In  this 
case  the  governor  on  the  cold-water  supply  should  be  set  for  a 
level  of  water  a  few  inches  below  the  level  which  operates  the  feed 
pump.  Otherwise  the  cold  water  might  be  let  into  the  heater  while 
the  pump  was  running  and  when  it  was  not  needed.  The  open 
heater  should  in  all  cases  be  provided  with  an  overflow  connected 
to  a  low-pressure  trap.  This  outlet  should  be  a  few  inches  above 


live  Steam. 


Supply  to' Heating  System. 


W////^///yM^///y//^ 

Figure  8— Arrangement  with  Open  Heater. 

the  water-line,  but  should  be  low  enough  to  prevent  the  possibility 
of  a  sudden  inflow  of  return  water  flooding  the  exhaust  pipes. 

With  the  arrangement  shown  in  Figure  7  the  cold  water  may  be 
supplied  by  a  pipe  running  direct  to  the  receiving  tank,  and  it  may 
be  regulated  by  hand,  according  to  the  level  of  the  water,  shown 
by  the  gauge  glass,  or  by  a  float  governor  similar  to  the  one  indi- 
cated on  the  open  heater  in  Figure  8. 

In  large  plants  also  there  are  frequently  two  or  more  feed  pumps, 
one  of  which  has  a  suction  connected  to  the  cold-water  supply,  or 
the  boilers  are  provided  with  injectors.  Further  details  of  piping 
will  be  discussed  in  a  subsequent  chapter. 

It  will  be  seen  that,  in  connection  with  the  open  heater,  the  re- 


26  STEAM  HEATING  AND  VENTILATION. 

ceiving  tank  is  merely  a  part  of  the  heater,  forming  an  additional 
reservoir  for  the  return  water.  It  is  possible  to  do  away  with  the 
tank  entirely,  connecting  the  returns  direct  into  the  water  cham- 
ber of  the  heater,  but  as  the  water  space  of  the  heater  is  generally 
comparatively  limited,  the  water  level  in  such  cases  is  subject  to 
more  or  less  extreme  fluctuations,  due  to  the  fact  that  the  return 
water  does  not  always  come  back  with  a  uniform  flow.  This  is 
especially  the  case  with  large  office  buildings,  when  the  building 
is  being  heated  in  the  morning  and  a  number  of  cold  radiators  are 
apt  to  be  turned  on  at  nearly  the  same  time.  In  the  same  way  it 
is  possible  also  to  do  away  with  the  receiving  tank  represented  in 
Figure  7,  but  this  is  subject  to  the  same  objection  as  in  the  other 
case,  only  to  a  more  extreme  degree,  as  the  small  governor  pro- 
vides scarcely  any  reservoir  volume  for  the  return  water  and  the 
pump  is  subject  to  sudden  changes  in  speed.  In  the  arrangement 
shown  in  Figure  7  the  main  return  pipe  is  generally  connected  at 
the  point,  F,  and  not  directly  to  the  tank. 

The  writer  has  installed  a  number  of  large  plants  with  open 
heaters  and  no  receiving  tanks  whatever  which  have  given  perfect 
satisfaction;  and  recently  installed  a  plant  having  over  16,000 
square  feet  of  radiating  surface  with  practically  the  same  arrange- 
ment as  indicated  in  Figure  7,  but  without  any  receiving  tank. 
This  system  requires  rather  careful  attention,  especially  in  the 
early  morning,  but  it  was  impracticable  on  account  of  local  condi- 
tions to  put  in  a  receiving  tank,  and  the  system  has  given  thorough 
satisfaction. 

It  should  be  noted  here  that  the  system  represented  in  Figure  8 
is  practically  a  gravity  system,  the  heater  and  tank  taking  the 
place  of  the  boiler  represented  in  Figures  1  to  4,  and  acting  both 
as  steam-producing  chamber  and  reservoir  for  return  water,  both 
being  at  this  point  under  precisely  the  same  pressure.  The  water 
level  in  the  return  pipes  and  return  risers  will  stand  at  a  higher 
level  than  in  the  heater  or  boiler  in  the  case  of  Figures  1  to  4,  by 
a  distance  representing  the  difference  in  pressure  required  to  force 
the  steam  through  the  system,  just  as  in  the  ordinary  gravity  sys- 
tem. As  a  matter  of  fact,  also,  it  is  found  that  in  the  system 
shown  in  Figure  7  the  pump  operates  much  more  smoothly  and 
;uniformly  if  the  system  is  made  a  gravity  system  by  connecting 
a  small  equalizing  steam  pipe  between  the  main  steam  supply  of 
-the  heating  system  and  the  top  of  the  receiving  tank  and  governor. 


STEAM  HEATING  AND  VENTILATION.  27 

If  the  plant  referred  to  operates  without  a  tank  this  equalizing 
pipe  is  found  to  be  practically  a  necessity.  In  any  case  an  equaliz- 
ing pipe  above  the  water  line  between  the  heater  and  its  tank,  or 
the  heater  and  the  governor,  is  necessary  to  maintain  the  same, 
pressure  upon  the  water  in  the  tank  as  exists  elsewhere  in  the  re- 
turn-water reservoirs. 

The  water-line  of  the  heating  system  sometimes  becomes  an 
important  consideration,,  especially  when  it  is  desired  to  place 
radiators  in  the  basement  of  a  building.  If  these  are  set  so  low 
that  the  return  water  is  liable  to  rise  above  the  connections,  the 
radiators  will  fill  with  water  when  turned  on,  which  will  prevent 
the  steam  from  circulating  into  the  radiator  and  will  be  sure  to 
give  trouble  from  water-hammer.  Besides  this,  with  anything 
except  the  overhead-supply  systems,  the  water  from  the  returns 
will  back  through  the  radiator  and  run  down  the  supply  riser,  and 
it  is  therefore  generally  necessary  to  set  radiators  several  feet 
above  the  water-line,  according  to  the  maximum  pressure  which 
is  necessary  to  create  circulation  of  steam  through  the  system  in 
coldest  weathp*  If  the  system  is  designed  for  very  low  pressure, 
1  or  2  pounds,  the  radiator  may  be  placed  within  4  feet  of  the 
water-line,  but  should  never  be  lower  than  this,  especially  in 
parts  of  the  building  far  removed  from  the  heater.  For  this 
reason  basements  are  usually  heated  by  steam  coils  suspended  from 
the  ceiling  or  placed  on  the  walls,  near  the  ceiling,  although  radi- 
ators are  sometimes  put  on  brackets  attached  to  the  walls;  fre- 
quently, in  order  to  lower  the  water-line,  the  pump,  governor,  and 
heater  also,  when  the  open  heater  is  used,  are  placed  in  a  pit.  There 
are,  however,  special  arrangements  of  radiator  connections  which, 
may  be  used  with  safety,  even  though  they  are  set  below  the  water 
line.  These  are  discussed  in  the  chapter  on  radiators. 

There  are  many  combined  automatic  pumps  and  receivers  de- 
signed for  taking  care  of  the  return  water  which  are  very  satis- 
factory, but  all  work  on  the  same  principle  of  a  tank  with  a  float 
governor  to  operate  the  pump.  There  are  also  automatic  traps  de- 
signed to  return  the  water  of  condensation  from  the  exhaust-steam 
heating  systems,  without  using  a  pump,  direct  to  a  high-pressure 
boiler  by  means  of  an  ingenious  combination  of  float  valves,  traps, 
reservoirs  and  check  valves,  and  some  of  these  work  with  consid- 
erable satisfaction  if  carefully  watched  and  kept  in  good  repair. 

In  many  mills  and  factories  which  use  condensing  engines,  and 


28  STEAM  HEATING  AND  VENTILATION. 

in  which,  consequently,,  exhaust  steam  is  not  readily  available  for 
heating,  steam  for  this  purpose  is  taken  direct  from  the  boilers 
through  a,  reducing  pressure  valve  and  used  in  the  heating  system 
at  a  pressure  of  5  to  20  pounds  per  square  inch.  In  such  systems 
the  water  is  generally  returned  to  the  boilers  by  an  automatic  pump 
and  receiver,  or  by  one  of  the  special  styles  of  traps  referred  to, 
which  for  operating  at  such  pressures  can  be  made  much  simpler 
than  when  used  for  the  extremely  low  pressure  of  the  ordinary 
exhaust  systems. 

Vacuum  systems. — As  a  refinement  of  exhaust-steam  heating 
there  has  been  developed  within  the  last  decade  what  is  known  as 
vacuum  systems  of  steam  heating,  the  object  of  these  being  to  ex- 
haust the  air  from  the  system  by  artificial  means  so  that  circulation 
may  be  effected  at  atmospheric  pressures  with  absolutely  no  back 
pressure  on  the  exhaust  pipes  from  the  engines.  There  are  two 
distinct  forms,  one  known  as  the  Paul  system,  the  other  as  the 
Webster.  The  former  system  provides  each  radiator  with  an  auto- 
matic air  valve  of  special  construction  and  connects  a  very  small 
pipe,  usually  |  inch,  to  each  of  these  valves,  bringing  them  together 
in  pipes  of  proper  size  in  the  basement  of  the  building,  and  con- 
necting to  a  special  exhauster,  which  maintains  a  constant  suc- 
tion on  the  entire  system  of  air  piping.  The  steam  and  return 
pipes  for  this  system  are  entirely  independent  of  the  air  pipe  and 
it  may  be  installed  on  any  of  the  systems  previously  mentioned. 

The  Webster  system  operates  on  an  entirely  different  principle, 
in  that  it  employs  an  automatic  air-and-water  valve  at  the  return 
outlet  of  the  radiator.  This  thermostatic  valve,  as  it  is  called,  is 
constructed  on  a  principle  much  like  the  automatic  air'  valve,  but 
is  of  larger  proportions.  It  is  adjusted  so  that  it  closes  automati- 
cally when  it  comes  in  contact  with  the  steam  temperature,  and 
opens  when  water  or  air  collects  about  it,  and  the  temperature  is 
reduced.  The  system  is  necessarily  a  two-pipe  system,  the  returns 
being  connected  to  these  thermostatic  valves,  but  no  other  air 
valves  or  air  piping  are  used.  The  return  pipes  are  connected  in 
the  basement  to  a  vacuum  pump  which  puts  a  strong  suction  on 
the  returns,  and  by  means  of  which  both  air  and  water  are  drawn 
through  the  thermostatic  valves,  the  water  being  delivered  by  the 
vacuum  pump  to  an  open  heater  or  receiving  tank,  while  the  air 
is  separated  by  an  automatic  device.  The  return  pipes  of  this 
system  are  very  small,  just  sufficient  to  take  care  of  the  water,  no 


STEAM  HEATING  AND  VENTILATION.  29 

steam  being  allowed  to  circulate  in  them.  The  steam  mains,  where 
necessary,  are  drained  into  the  return  pipes  through  thermostatio 
valves.  The  return  mains  being  under  suction,  and  having  110 
direct  connection  with  the  steam  pipes,  can,  a  certain  extent, 
be  run  independent  of  the  usual  necessity  of  draining  by  gravity, 
in  some  cases  the  water  being  lifted  out  of  radiators  placed  below 
the  return  -mains. 

In  the  Union  Depot  at  Columbus,  Ohio,  which  is  equipped  with 
this  system,  the  radiators  in  the  basement  are  about  13  feet  below 
the  supply  and  return  mains,  which  run  parallel  along  the  base- 
ment ceiling,  and  the  return  water  is  drawn  up  out  of  the  radiators 
without  any  water-hammer  or  other  inconvenience. 

A  modification  of  the  Paul  system  was  recently  installed  in  a 
large  office  building  in  Chicago  which  has  given  decided  satisfac- 
tion. Instead  of  the  air  valve  on  each  radiator,  a  small  tee  with 
an  aperture  only  1/16  inch  in  diameter  was  screwed  into  the  air 
hole  of  the  radiator,  and  these  connected  together  into  a  system 
of  small  air  pipes  running  to  an  air  pump  or  exhauster.  This 
maintains  a  constant  suction  on  the  air  holes.  Although  there  is 
apparently  a  continual  leakage  of  steam  in  this  system,,  it  is  not 
more  than  with  the  automatic  air  valves,  as  the  latter  are  seldom 
maintained  in  perfect  adjustment.  The  tees  were  made  writh  a 
plug  on  the  outside  which  could  be  removed  for  the  purpose  of 
cleaning  the  pin-hole  by  means  of  a  wire. 

Plants  equipped  with  vacuum  systems  frequently  operate  slight- 
ly below  the  atmospheric  pressure,  and  besides  entirely  doing 
away  with  back  pressure  on  engines  and  removing  the  air  from 
the  system,  there  are  many  incidental  advantages  in  the  operation 
of  plants  of  this  character  which  will  lead  to  a  very  extended 
adoption.  The  principal  objection  to  vacuum  systems  lies  in  the 
fact  that  the  exhausters  or  vacuum  pumps  take  considerable  live 
steam  to  operate  them,  and  almost  as  much  in  moderate  weather 
as  on  very  cold  days. 

The  recent  development  of  vacuum  pumps,  however,  has  been 
of  great  value  to  steam-heating  work.  Pumps  of  this  class  are 
now  made  which  will  not  run  away  when  all  the  water  is  pumped 
out  of  the  suction,  the  water  end  of  the  pump  receiving  only  air 
and  steam.  They  will  run  along  slowly  under  such  conditions, 
taking  care  of  the  water  as  it  comes.  If  a  pump  of  this  descrip- 
tion is  connected  to  the  lower  point  of  the  main  return  from 


30  STEAM  HEATING  AND  VENTILATION. 

e  heating  system,  it  can  be  made  to  maintain  what  is  now  called 
a  dry  return.  This  is  in  some  cases  valuable,  as  it  obviates  the 
necessity  of  considering  the  water-line,  as  before  mentioned,  in 
placing  radiators  in  basements.  Vacuum  pumps  used  in  this  way 
are  especially  valuable  in  cases  where  return  water  is  to  be  brought 
l>ack  from  a  heating  system  at  some  distance  from  the  source  of 
steam  supply. 


CHAPTEE  III.— STEAM-HEATING  APPARATUS. 

Boilers. — The  questions  of  boiler  design,  construction,  setting, 
etc.,  involve  so  many  considerations  requiring  careful  scientific 
study,  that  the  entire  problem  is  omitted  from  this  work  and  the 
reader  is  referred  to  the  valuable  treatises  devoted  exclusively  to 
the  subject.  There  is,  however,  one  kind  of  boiler  which  should  be 
given  some  special  mention- in  this  place.  This  is  the  self-contained 
cast-iron  sectional  boiler  which  is  used  only  for  small,  low-pressure 
gravity-heating  systems  in  residences.  These  boilers  are  built  up 
in  sections  of  various  shapes  bolted  together,  the  joints  being  kept 
tight  merely  by  the  pressure  caused  by  the  bolts.  On  account  of 
their  material,  as  well  as  the  method  of  construction,  they  are 
not  adapted  for  anything  but  very  low  pressures.  For  the  larger 
plants  in  which  cast-iron  boilers  are  used,  it  is  better  to  install 
two  small  ones  than  to  attempt  to  use  one  large  one,  as  it  gives 
better  economy  in  operation,  and  there  is  less  danger  of  accident 
to  small  boilers  than  to  those  with  large  castings. 

In  selecting  these  boilers  it  should  always  be  borne  in  miud 
that  the  demands  of  commercial  competition  cause  them  to  be 
very  generally  overrated  by  their  makers,  so  that  in  choosing  sizes 
from  catalogues  it  is  advisable  to  make  considerable  reduction  from 
the  rated  capacities.  Mr.  James  R.  Willett,  in  a  pamphlet  on  the 
heating  and  ventilating  of  residences,  gives  the  accompanying  table 
for  the  sizes  of  cast-iron  boilers.  Where  boilers  of  the  kinds  used 
for  steam  power  are  employed  in  simple  heating  plants  of  large 
size — of  which  there  are  to-day  but  few — there  is  an  old  rule  for 
proportioning  the  size,  to  the  effect  that  there  must  be  1  square 
foot  of  boiler  surface  to  10  square  feet  of  radiating  surface.  This 
rule  when  applied  to  a  boiler  with  a  well-designed  furnace,  stack 
and  setting  should  be  very  conservative.  It  is  much  better  to 
estimate  the  steam  consumption  of  the  entire  plant  (see  Chapter 
V.,  page  60  for  steam  consumption  of  radiation)  and  calculate 
the  boiler  requirements  according  to  the  rules  of  boiler  design. 
The  designs  of  the  cast-iron  heating  boilers  are  innumerable  and 


32 


STEAM  HEATING  AND  VENTILATION. 


can  only  be  selected  by  the  careful  judgment  of  the  engineer.  The- 
chief  points  to  be  considered  -are  efficiency  of  heating  surface  and 
capacity  of  grate  in  proportion  to  surface,  strength  of  parts,  tight- 
ness of  joints,  ease  of  cleaning  and  effectiveness  of  circulation — 
there  should  be  no  "dead  ends"  where  the  water  is  not  kept  in 
circulation  by  the  heat  of  the  fire. 

Willett's  Table  of  Cast-iron  Boiler  Capacities. 

Radiators;  Area  of  boiler  Radiators;  Area  of  boiler 

total  sq.  ft.  grate  in  sq.  in.  total  sq.  ft.  grate  in  sq.  in. 

400  500  1,600  1,420 

500  580  1,800  1,560 

600  650  2,000  1,700 

700  740  2,250  1,880 

800  820  2,500  2,020 

900  890  2,750  2,230 

1,000  970  3,000  2,400 

1,200  1,120  3,500  2,770 

1,400  1,270  4,000  3,120 

There  might  also  be  classed  under  the  head  of  steam-heating 
apparatus  the  various  traps,  automatic  receivers  and  other  special 


4pt 


iiiliiiHaa 


Fio.9 


FiG.IO  FIG. II 

One,  Two  and  Three  Column  Radiators. 


appliances  which  are  used — especially  in  connection  with  exhaust 
heating — for  returning  the  water  of  condensation  to  the  boiler, 
and  which  were  described  in  the  preceding  chapter.  But  besides 
these  the  only  apparatus  pertaining  to  a  heating  system  without 


STEAM  HEATING  AND  VENTILATION. 


33 


mechanical  ventilation  are  the  radiators,  and  in  the  design  of  the 
system  the  rtmost  consideration  should  be  given  to  their  selection 
and  proportioning. 

Radiators. — Radiators  are  made  either  of  cast  or  wrought  iron 
and  are  classified  according  to  kind  of  heating  for  which  they  are 
used  into  direct,  direct-indirect,  and  indirect  radiators.  A  few 
years  ago  wrought-iron  pipe  made  up  with  bends  and  headers  into 
coils  of  various  sizes  and  shapes  was  used  very  largely  for  radia- 
tors, and  especially  for  indirect  radiators;  but  on  account  of  their 
greater  economy  of  construction,  cast-iron  radiators  are  rapidly 
supplanting  the  wrought-iron  pipes  for  all  purposes.  To-day 


FIG.  12 


wrought-iron  pipe  coils  are  used  in  direct  heating  where  very  large 
radiators  are  required  spread  over  a  large  area  of  wall  surface., 
such  as  in  factory  rooms  or  warehouses,  where  a  series  of  long^ 
pipes  connected  into  headers  at  each  end  are  run  along  the  walls-, 
either  over'or  under  the  windows,  preferably  under.    Pipe  coils  are- 
also  used  for  large  indirect  radiators,  but  in  this  case,  as  a  rule, , 
only  in  connection  with  ventilating  fans,  as  will  be  described  in 
subsequent  chapters. 

The  styles  and  kinds  of  cast-iron  radiators 'are  innumerable.. 
They  are  made  in  sections  or  loops,  which  are  fastened  together 


34  STEAM  HEATING  AND   VENTILATION. 

by  pipe  nipples  of  various  kinds,  with  a  paper  or  thin  metal  gasket 
between  the  faced  surfaces  of  the  joint.  These  nipples  are  some- 
times threaded  and  screwed  up  tight  by  special  wrenches,  but  what 
is  known  as  the  push-nipple  is  extensively  used.  These  nipples 
are  not  threaded  but  are  turned  to  a  close  fit  with  the  holes  in  the 
loops,  at  the  joint,  which  are  bored  out  perfectly  true,  and  they  are 
driven  tight  by  pressure  with  jacks  or  presses  made  for  the  pur- 
pose. 

Cast-iron  radiators  are  classified  according  to  the  kind  of  sur- 
face, into  plain-surface  and  extension-surface  radiators,  and  ac- 
cording to  their  style  of  construction  into  open  and  flue  radiators, 
&nd  of  the  open  one,  two,  three  and  four  column  type,  according 
to  the  formation  of  the  loops.  The  different  classifications  will  be 
better  understood  from  inspection  of  the  accompanying  illustra- 
tions. The  extension-surface  radiators,  Figures  14  and  18,  as 
the  name  implies,  have  extensions  of  various  kinds  in  the  form  of 
ridges  or  pins  cast  on  to  the  otherwise  plain  surface,  and  are  used 
principally  for  indirect  radiators.  The  flue  radiators,  Figure  1C, 
are  used  extensively  for  direct-indirect  radiation,  but  for  such  pur- 
pose are  provided  with  shields  and  provision  of  some  kind  for  con- 
nection with  the  outer  air.  Flue  radiators,  such  as  shown  in  Fig- 
ures 12  and  13,  are  sometimes  spoken  of  as  veiled-surface  radiators. 
Most  low  radiators  of  considerable  width  in  proportion  to  the 
lieight  are  of  the  flue  type.  The  radiator  that  has  been  used  for 
direct  radiation  much  more  widely  than  any  other  is  the  two- 
column  plain-surface  radiator,  such  as  is  shown  in  Figure  10,  but 
the  numerous  other  forms  are  being  more  and  more  extensively 
introduced. 

.  Most  radiators  for  steam  heating  have  all  the  loops  connected 
by  only  one  steam  passage  through  the  bottom,  but  some  are  also 
connected  at  the  top  as  well.  Such  radiators  are  adapted  to  steam 
heating  from  hot-water  heating  practice,  as  they  are  the  only 
kind  that  can  be  used  in  the  latter,  and  are  hence  known  as  the 
hot-water  type.  See  Figure  20.  Almost  all  low  and  wide  steam 
radiators  are  made  in  this  way,  and  by  some  authorities  this  con- 
struction is  preferred  in  all  kinds.  Further  discussion  of  this  sub- 
ject will  be  taken  up  later. 

Measuring  radiators. — Eadiators  are  universally  rated  by  the 
number  of  square  feet  of  surface  which  they  contain.  This,  at  the 
present  time,  is  for  many  reasons  a  very  arbitrary  method  and 


STEAM  HEATING  AND  VENTILATION. 


holds  chiefly  for  want  of  a  better.  The  main  difficulty  lies  in  the 
great  difference  in  the  value  of  the  various  kinds  of  surfaces,  no 
distinction  being  made  in  such  rating  between  plain,  extension  or 
veiled  surface.  The  variation  is  enhanced  also  by  the  fact  that 
radiators  are  to  a  large  extent  overrated,  especially  in  the  less  com- 
mon sizes  and  styles;  and  owing  to  the  difficulty  of  accurately 
measuring  the  surface,  this  fact  is  very  generally  overlooked.  A 
number  of  methods  have  been  proposed  and  tried  for  measuring 
the  surface  of  radiators  which  are  made  in  ornamental  design  and 
with  all  kinds  of  irregular  surfaces.  In  the  course  of  a  large  ex- 
perience with  radiators  of  all  kinds,  the  author  tried  many  different 
methods  and  finally  devised  one  which  he  has  found  comparatively 


;® 


Fio.15 


Direct 


FIG.  16 

Indirect   Radiators. 


FIG.  17 


THE  ENGINEERING 


simple  and  very  reliable.  By  this  method  all  irregular  surfaced  are 
measured  by  covering  them  with  very  thin  flexible  paper  which 
must  be  carefully  turned  and  folded  into  all  irregularities  of  the 
surface.  After  being  thus  fitted,  the  paper  should  be  rubbed  by 
blackened  fingers.  They  are  generally  sufficiently  soiled  for  the 
purpose  from  handling  the  radiators.  In  this  way  when  the  paper 
is  spread  out,  the  part  that  was  folded  under  can  be  readily  distin- 
guished, and  the  actual  area  of  the  surface  can  be  determined  by 
measuring  the  blackened  parts  with  a  planimeter.  In  lieu  of  a 
planimeter,  thin  cross-section  paper  can  be  used  and  the  areas  de- 
termined by  counting  the  small  squares.  In  measuring  up  a  ra- 
diator loop,  it  is  best  to  divide  the  surface  by  thin  lines  of  white 
chalk  or  paint  and  measure  each  division  separately.  The  parts 


36 


STEAM  HEATING  AND  VENTILATION. 


that  have  a  uniform  cross-section,  as  the  columns  of  most  direct 
radiators,  can  be  measured  by  determining  the  actual  circumfer- 
ence of  the  surface  by  fitting  a  paper  around  it  and  multiplying 
this  by  the  length  of  the  column.  It  was  once  objected  to  this 
method  that  it  does  not  take  into  account  the  effect  of  the  raised 
ornamentation  on  a  radiator.  This  is  not  the  case,  or  at  least  any 
ornament  that  it  does  not  take  into  account  would  not  increase 
the  total  surface  to  an  appreciable  degree.  Measurements  of  ra- 
diators by  this  method  by  different  observers  acting  independently 
have  been  found  to  check  within  less  than  I  per  cent. 


FlO.18   Indirect    Radiator. 


Action  of  radiators. — Before  proceeding  further  in  the  discussion 
of  radiators,  it  may  be  well  to  consider  some  of  the  principles  which 
govern  their  operation  in  practical  use.  The  fundamental  prin- 
ciple of  their,  operation  is  undoubtedly  the  axiomatic  theory  that 
there  is  a  universal  tendency  toward  the  equalization  of  tempera- 
ture; in  other  words,  that  hot  bodies  give  up  their  heat  to  the 
colder  ones  which  surround  them.  In  general  this  is  accomplished 
by  three  different  processes,  namely:  conduction,  convection  and 
radiation,  the  word  radiation  being  used  here  in  the  special  sense 
of -radiant  heat.  These  may  best  be  defined  by  illustrations.  When 
one  part  of  a  rigid  body  is  in  contact  with  a  warmer  body  heat 
passes  or  flows  from  the  latter  through  the  former  to  its  cold  por- 


STEAM  HEATING  AND   VENTILATION. 


37 


lions  as  long  as  there  is  any  difference  of  temperature.  This  is 
conduction  of  heat,  and  the  rate  of  flow  under  the  same  conditions 
of  temperature  varies  as  a  factor  known  as  the  heat  conductivity 
of  the  body  concerned.  The  heat  conductivity  of  fluids,  liquids 
and  gases  is  very  low,  practically  zero,  but  heat  is  transferred  in 
them  by  convection.  The  particles  in  direct  contact  with  the 
source  of  heat  are  heated  above  the  temperature  of  the  rest,  and  an 
increase  in  temperature  of  any  liquid  or  gas  invariably  decreases 


p 

ujy 


FIG.  2O  Hot-  Water  and  Steam  Pipe  Loops. 

THE  IKCJNttHIHQ  BA££Q, 

its  specific  gravity  and  causes  an  upward  current  of  the  hot  parti- 
cles, which  brings  the  colder  particles  in  turn  in  contact  with  the 
hot  body,  thus  maintaining  a  circulation  which  tends  to  raise  the 
temperature  of  the  entire  mass.  Eadiation  or  radiant  heat  is  en- 
tirely different  from  either  of  -these  in  its  action.  It  is  a  wave 
motion  and  travels  through  air  and  all  transparent  bodies  with 
the  velocity  of  light  without  heating  them,  and  only  appears  as 
sensible  heat  when  its  course  is  interrupted  by  opaque  bodies  by 
which  it  is  absorbed.* 

*Some  bodies  which  are  quite  opaque  to  light  waves  are  more  or  less 
transparent  to  heat  waves,  and  vice  versa,  and  nothing  except  the  im- 
material ether  is  absolutely  transparent  to  them.  The  earth's  atmos- 
phere absorbs  a  considerable  amount  of  the  radiant  heat  from  the  sun. 


38  STEAM  HEATING  AND  VENTILATION. 

A  radiator  gives  out  its  heat  to  its  surroundings  by  radiation  to 
the  walls  and  objects  and  by  convection  to  the  air.  What  propor- 
tion is  given  out  in  each  way  it  is  difficult  to  measure  in  any  case 
and  depends  principally  on  the  construction  of  the  radiator  and 
the  way  it  is  set,  but  also  more  or  less  upon  the  conditions  of  tem- 
perature, nature  of  surface,  etc.  Peclet,  the  great  French  physi- 
cist, in  the  middle  of  the  century,  fully  investigated  the  laws  of  ra- 
diant heat  as  well  as  those  of  convection  in  still  air.  The  formulas 
which  he  deduced  are  applicable  only  in  a  limited  degree  to  ra- 
diator practice.  His  investigations,  as  well  as  those  of  others  since 
that  time,  showed  that  for  a  single  iron  pipe  in  still  air*  under 
conditions  of  temperature  which  prevail  in  radiator  practice,  the 
heat  given  off  as  radiant  heat  is  just  about  equal  to  that  given  out 
by  convection. t 

But  radiators  are  invariably  built  of  clusters  of  pipes  or  sur- 
faces, and  as  radiant  heat  travels  only  in  straight  lines  and  per- 
pendicular to  the  surface  of  its  source,  a  large  proportion  of  the 
surface  is  wasted  so  far  as  radiant  heat  is  concerned,  due  to  what 
may  be  called  the  mutual  interception  of  the  rays.  In  the  ordi- 
nary one-column  cast-iron  radiator,  the  proportion  of  surface  from 
which  no  radiant  heat  takes  place  is  nearly  20  per  cent.,  in  the 
two-column,  45  to  55  per  cent,  and  in  the  three-column,  55  to  65. 
Assuming  that  the  radiant  heat  amounts  to  one-half  the  total,  the 
reduction  of  heat  emitted  would  be  one-half  of  these  percentages. 
Another  fact  which  further  reduces  the  radiant  heat  is  that  ra- 
diators are  usually  set  very  close  to  a  wall  which  becomes  heated 
to  a  comparatively  high  degree  and  consequently  radiates  back  a 
large  portion  of  the  heat  to  the  wall  side  of  the  radiator.  This  is 
true  to  an  extreme  degree  in  the  case  of  indirect  radiators  which 
are  enclosed  in  boxes  of  wood  or  sheet  metal  and  are  not  located  in 
the  room  they  are  to  warm.  With  these  the  heating  is  accom- 
plished entirely  by  convection,  while  with  direct  radiators  the  ra- 
diant heat  rarely  amounts  to  40  per  cent.,  generally  not  over  30, 
and  often  in  practice  considerably  less.  For  a  radiator  in  any  par- 
ticular location  the  radiant  heat  is  constant  for  the  same  conditions 

*By  "still  air"  in  this  sense  is  meant  the  air  of  a  room  in  which  there 
are  no  currents  except  those  created  by  a  column  of  hot  air  rising  from 
the  heated  surface. 

tFor  a  complete  account  of  Peclet's  experiments  and  his  results  see 
"A  Treatise  on  Heat"  by  Thos.  Box;  London:  E.  &  T.  N.  Spon. 


STEAM  HEATING  AND  VENTILATION.  39> 

of  temperature  of  the  radiator  and  surrounding  objects,  and  is  in- 
dependent of  currents  of  air.  This  is  by  no  means  the  case  with 
the  convected  heat,  which  is  increased  greatly  by  a  slight  draft 
from  any  extraneous  source.  In  this  connection  it  is  very  remark- 
able what  a  great  effect  an  almost  imperceptible  draft  will  have  on 
the  heat  given  out  by  a  radiator.  This  is  partly  due  to  the  lower- 
ing of  the  temperature  of  the  air  between  the  loops,  but  also  to  the 
fact  that  with  the  same  temperatures  any  increase  in  velocity  in- 
creases the  amount  of  heat  the  air  absorbs. 

Radiator  tests. — Numerous  tests  of  radiators  have  been  made 
since  those  of  Mills,  Eichards  and  others  in  the  early  '70's,  bur 
there  is  a  wide  variation  in  the  results  obtained,  due  partly  to  the 
different  kinds  of  radiators  tested  and  partly  to  the  different  meth- 
ods of  testing.  As  yet,  no  standard  means  of  testing  radiators  has 
been  adopted.  The  steam  radiator  as  a  heat-using  device  is  theo- 
retically perfect;  that  is,  all  of  the  heat  that  is  put  into  the  ra- 
diator by  the  latent  heat  of  the  steam  condensed  is  given  out  to 
the  air  and  objects  surrounding.  Its  efficiency  is  therefore  100 
per  cent.  The  question  of  practical  efficiency  is,  therefore,  more 
strictly  speaking,  only  one  of  effectiveness  of  surface.  That  is, 
of  two  radiators  under  exactly  the  same  conditions  of  tempera- 
ture and  surroundings,  that  one  which  has  such  an  arrangement  of 
its  surfaces  as  to  give  out  the  most  heat  per  square  foot  is  the 
most  effective,  usually  called  the  most  efficient.  In  all  tests  of 
radiators,  the  heat  given  off  is  measured  by  connecting  them  so 
that  the  steam  which  condenses  can  be  accurately  weighed,  its 
pressure,  quality  and  temperature  being  determined  at  the  same 
time.  The  results  are  generally  reduced  to  British  thermal  units 
given  off  per  square  foot  per  hour  per  degree  difference  of  tem- 
perature between  the  air  of  the  room  and  the  steam  of  the  ra- 
diator. 

Tests  of  radiators  have  been  made  in  various  ways  by  Mr.  George 
H.  Barrus,  by  Profs.  Denton  and  Jacobus  of  the  Stevens  Institute, 
by  Prof.  R.  C.  Carpenter,  of  Sibley  College,  Cornell  University, 
and  by  the  author.  The  results  of  Prof.  Carpenter's  tests  are  pub- 
lished in  detail  in  his  valuable  work  on  "Heating  and  Ventilation 
of  Buildings.''  In  these  tests  the  radiators  were  located  in  sepa- 
rate compartments,  7  xlO  feet,  built  together  in  a  large  room,  and 
as  shown  in  Figures  21  and  22.  In  order  to  allow  some  circulation 
of  air  so  that  the  temperature  of  air  of  the  compartments  might 


40 


STEAM  HEATING  AND  VENTILATION. 


not  get  as  high  as  that  of  the  radiators,  small  openings  were  made 
in  each  at  the  bottom  and  top.  In  1895  and  1896  the  author  had 
occasion  to  make  comparative  tests  of  a  large  numher  of  radiators 
of  various  kinds  and  types,  and  the  arrangement  used  by  him  for 
testing  is  shown  in  Figures  23  to  25.  The  two  test  rooms  were 
built  in  the  main  floor  of  a  large  warehouse,  and  each  was  15  feet 
by  11  feet  8  inches,  and  extended  to  the  ceiling,  15  feet  5  inches 
high.  The  walls  of  the  test  rooms  were  built  of  matched  and 
beaded  pine  and  lined  with  lapped  courses  of  heavy  building  paper. 
The  warehouse  room  in  which  the  test  rooms  were  located  was 


Fl  G.  2 1  Prof. Co  rpente  r's  Arrangement  for  Testing  Radiators. 


about  85  by  50  feet,  with  brick  walls  on  both  sides  and  wood  and 
glass  partitions  at  each  end.  Neither  end  of  this  large  room,  how- 
ever, was  open  to  the  outside  air  and  the  side  walls  were  party 
walls.  Every  effort  was  made  to  keep  the  air  of  the  test  rooms 
free  from  all  drafts  except  those  induced  by  the  column  of  hot  air 
rising  from  the  radiators  and  to  otherwise  make  the  conditions  as 
nearly  as  possible  those  of  actual  practice.  To  permit  some  cir- 
culation in  the  test  room,  so  that  the  air  would  not  get  too  hot, 
an  opening  4  inches  long  and  1 8  inches  high  was  cut  in  the  front 


STEAM  HEATING  AND  VENTILATION. 


41 


wall  at  the  floor,  and  to  prevent  direct  drafts  on  the  radiators, 
those  openings  were  surrounded  inside  by  a  wooden  screen,  2  feet  8 
inches  high.  The  front  partition  was  also  opened  18  inches  at  the 
ceiling.  The  piping,  as  shown  in  Figure  25,  was  arranged  so  that 
the  steam  was  supplied  to  the  radiators  on  what  is  known  as  the 
one-pipe  overhead  system.  Steam  was  supplied  to  the  separator 
at  a  pressure  of  2  or  3  pounds  above  atmosphere  through  a  2-inch 
pipe  from  a  small  heating  boiler.  The  pressure  carried  at  tho 
boiler  was  slightly  in  excess  of  that  on  the  separator,  it  being 
throttled  at  the  latter.  By  this  means  and  by  leaving  the  drip  on 
the  separator  slightly  opened,  the  steam  was  supplied  free  from 
all  entrained  moisture.  The  piping,  separator,  etc.,  were  all  care- 
fully covered.  The  heat  given  off  was  measured  by  drawing  off  the 
condensed  steam  from  the  drip  pots  into  cold  water  and  accurately 
weighing  it. 


FlG. 22  Prof  Carpenter's  Arrangement 
of  Each  Radiator  and  Compartment  Removed 


In  practically  all  of  the  tests  made  in  this  plant,  one  radiator 
was  used  as  a  standard  and  all  the  others  tested  and  compared  with 
it  In  each  test  the  radiators  were  connected  and  a  preliminary 
run  made  with  open  air-valves  until  the  conditions  became  con- 
stant and  uniform,  and  a  test  run  made  for  two  to  three  hours.  The 
radiators  were  then  interchanged  and  the  test  repeated.  Even 
with  these  precautions  it  was  only  by  exercising  the  greatest  care 
that  it  was  possible  to  obtain  results  which  checked  closely.  It  is 
very  remarkable  what  a  decided  effect  can  be  created  by  a  very 


42 


STEAM  HEATING  AND  VENTILATION. 


slight  motion  of  the  air  from  an  external  source.  Opening  a  door 
at  one  end  of  the  warehouse  room,  although,  as  before  stated,  these 
doors  did  not  open  outdoors,  made  a  decided  difference,  and  if  a 
strong  wind  was  blowing  outside,  the  radiator  to  the  windward  side 


Ceiling    of  Wardroom. . 


to-                  f      || 

Opening  for  Air. 

Door 
Opening 
for  Air. 

Door. 

'///v////////////////////////////////////////////////////////////  /////. 
FIG.  23  Front  Elevation  of  Testing  Rooms. 

Brick   Wail  of  Wareroom. 
ty//////////////////////////////////////////////////////////////////. 

Radiator 

Room   A. 
,  Partition  2'8"Hiqh  in  front 
(  of  Opening  at  Floor. 

\^—\       \ 

Radiator.  ^ 

so       Room     B. 
I 

FIG. 24-  Plan  of  Testinq  Rooms. 

Twe  EnoOiUniMO  P 

(Partition  between  Rooms. 
Floor  of  Testing  Room . 


rio.25  Elevation  of  Piping.Radiator Tests 


Dnp  Pot-^ 
4'Pipt.  IG'Lony. 


had  some  advantage,  although  no  draft  would  be  perceptible. 
However,  with  due  care,  the  two  tests  for  each  comparison  were 
made  to  check  with  fair  accuracy. 


STEAM  HEATING  AND  VENTILATION.  43 

The  radiator  used  as  the  standard  on  these  tests  was  an  ordinary 
cast-iron  two-column  steam  radiator,  38  inches  high,  with  but  little 
ornamentation.  The  writer  believes  that  this  is  the  only  way  of 
accurately  testing  radiators,  and  the  adoption  of  any  one  definite 
make  of  radiator  as  a  universal  standard  of  comparison  would  do 
much  to  extend  the  knowledge  of  the  comparative  effect  and  value 
of  radiators.  Tests  of  radiators  made  in  different  ways  or  in  dif- 
ferent locations  are  valueless  for  accurate  comparison.  But  all 
comparative  tests  made  against  the  same  standard  if  accurately 
and  carefully  carried  out,  could  be  compared  in  percentages  of  the 
heating  effect  of  the  standard  used.  The  writer  found  that  under 
tne  conditions  in  his  testing  plant  the  38-inch  two-column  cast- 
iron  radiator  used  as  a  standard  gave  out  1.60  British  thermal  units 
per  square  foot  per  hour  per  degree  difference  of  temperature  with 
an  average  steam  temperature  of  224  degrees  Fahr.,  and  aver- 
age temperatures  of  the  rooms  of  76.5  degrees.  The  average 
difference  of  temperatures  was  147.5  degrees. 

This  cofficient  of  1.6  B.  T.  U.  per  square  foot  per  hour  per  de- 
gree difference  of  tempt  ra~u~"2  between  the  steam  and  air  is  some- 
what lower  than  that  which  Prof.  Carpenter  obtained  for  a  ra- 
diator of  almost  the  same  size  and  design.  Assuming  that  the  ra- 
diators were  exactly  alike,  such  variation  as  there  was  can  be  due 
to  two  causes:  1,  a  variation  in  the  difference  of  temperature  be- 
tween the  steam  and  the  surrounding  room;  and  2,  the  mode  of 
setting  and  the  consequent  freedom  of  air  circulation  around  the 
radiator.  In  regard  to  the  first  cause,  all  tests  of  radiating  sur- 
faces from  Peclet  down  show  that  the  coefficient  is  greater,  the 
greater  the  difference  of  temperature,  and  for  extreme  variations 
in  the  difference  of  temperature,  the  coefficient  is  very  much  great- 
er than  in  the  limits  of  ordinary  radiator  practice,  with  steam  tem- 
peratures from  212  to  230  and  mean  air  temperatures  from  40 
to  70;  within  which  range  the  variation  in  the  coefficient  from 
this  cause  is  less  than  9  per  cent.  In  regard  to  the  second 
cause — the  freedom  of  the  air-circulation  around  the  radiator 
— this  is  by  far  the.  chief  cause  of  difference  in  action  of  radia- 
tors. Profs.  Denton  and  Jacobus  of  the  Stevens  Institute  of 
Technology  made  some  comparative  tests  of  radiators,  published 
in  The  Engineering  Pncord  of  September  8,  1894,  with  a  plant  very 
similar  to  that  used  by  the  author,  except,  besides  having  an  open- 
ing at  the  top,  there  was  in  each  of  the  test  rooms  an  outside  win- 


44  STEAM  HEATING  AND  VENTILATION. 

dow,  "which  was  opened  a  certain  amount  during  the  tests" — a 
dangerous  way,  the  author  believes,  to  test  radiators  with  the  ex- 
pectation of  jbtaining  checking  results — although  "a  screen  was 
placed  between  the  radiators  and  windows  to  prevent  direct  drafts 
from  striking  the  radiators/'  These  tests  were  unquestionably 
carefully  made  and  were  checked  by  reversing  the  position  of  the 
radiators,  so  that  the  comparative  results  obtained  may  be  taken 
as  reliable;  but  the  coefficients  were  in  the  neighborhood  of  20  per 
cent,  higher  than  that  obtained  by  the  writer  on  similar  radiators, 
due  entirely  to  the  greater  freedom  of  air-circulation  from  the 
open  windows.  This  is  a  matter  of  great  importance  in  practice 
and  in  consequence  the  results  obtained  in  radiator  tests  depend 
largely  upon  the  setting  of  the  radiator.  It  is  this  fact  also  which 
makes  a  radiator  to  some  extent  automatic  or  self -adjustable. 
Take  for  example,  an  ordinary  room  say  with  a  north  exposure  and 
one  direct  radiator  set,  as  they  generally  are  and  always  should 
be,  under  the  window.  On  a  moderately  cold  day  with  the  ther- 
mometer outside  at  20  degrees  and  the  wind  from  the  south  or 
east,  the  radiator  will  be  turned  on  the  entire  time.  On  another 
day  with  the  thermometer  outside  at  zero  and  the  wind  from  the 
north,  the  radiator  very  probably  keeps  the  room  at  the  same 
mean  temperature  with  practically  the  same  temperature  of  steam. 
The  reason  is  that  in  the  latter  case  the  cold  air  which  leaks  in 
through  the  walls  and  around  the  window  casing,  besides  keeping 
the  air  immediately  in  contact  with  the  radiator  at  a  lowpr  mean 
temperature,  causes  a  much  more  rapid  circulation  around  the  rad- 
iator, with  the  result  that  it  gives  out  more  heat  units  per  square 
foot.  It  is  for  this  reason,  too,  that  one  may  put  down  for  a  posi- 
tive and  infallible  rule  in  radiator  design  that  the  radiator  which 
has  the  most  open  space  around  its  surfaces  and  the  most  inter- 
rupted exposure  to  the  surrounding  air  will  give  out  the  most  heat 
per  square  foot  under  the  same  conditions  of  setting.  In  compliance 
with  this  rule,  other  things  being  equal,  narrow  radiators  are  more 
effective  than  wide  ones,  and  low  ones  than  high  ones;  but  the 
effect  of  width  and  height  can  more  than  be  offset  by  a  slight  in- 
crease in  the  distance  between  the  loops;  for  example,  the  author 
found  that  a  four-column  38-inch  radiator  gave  out  exactly  the 
same  heat  per  square  foot  of  measured  surface  as  a  two-column 
38-inch  radiator,  because  the  former  had  a  mean  distance  between 
the  loops  about  16/100  of  an  inch  greater  than  the  latter;  also  a 


STEAM  HEATING  AND  VENTILATION.  45 

38-inch  flue  radiator  was  improved  7  per  cent,  in  heating  effect  by 
separating  the  loops  %  inch. 

It  is  largely  for  this  reason  of  freer  circulation  around  the  sur- 
face that  the  ordinary  wall  coils  of  1  or  l^-inch  wrought-iron 
pipe,  which  are  extensively  used  in  factories,  are  much  more  ef- 
fective than  cast-iron  radiators.  Some  careful  tests  by  Prof.  M. 
E.  Cooley  of  the  University  of  Michigan  showed  that  a  single  layer 
coil  of  horizontal  pipes  gives  out  40  per  cent,  more  heat  per  square 
foot  than  a  two-column  cast-iron  radiator  under  the  same  condi- 
tions of  setting. 

It  may  be  further  stated  in  compliance  with  the  same  rule  that 
the  hot-water  type  of  radiators  is  somewhat  less  effective  than  the 
steam  type  on  account  of  the  obstruction  offered  by  the  loop  con- 
nection at  the  top,  and  also  that  flue  radiators  are  less  effective 
than  the  ordinary  open  type.  Just  how  much  less  effective  the 
flue  types  are  depends  upon  the  kind  and  design,  but  the  wide  low 
flue  radiators,  not  considering  extension-surface  types,  are  some- 
times over  23  per  cent,  less  effective  than  the  ordinary  two-column 
radiators  of  the  same  height.  It  may  also  be  stated  that  there  is 
a  greater  difference  between  the  high  and  low  radiators  of  the  flue 
type  than  of  the  open  types.  One  make  of  two-column  cast-iron 
radiator  proved  6^  per  cent,  more  effective  in  the  20-inch  height 
than  in  the  38-inch,  and  another  make  nearly  10  per  cent.,  while 
an  8-inch  wide  flue  radiator  showed  over  20  per  cent,  improvement 
in  the  20-inch  over  the  38-inch. 

Condensation  at  different  pressures. — Mr.  W.  J.  Baldwin  made 
some  tests  some  years  ago  to  determine  the  relative  heating  effect 
of  radiators  under  different  steam  pressures,  with  the  same  con- 
ditions of  setting.  Taking  the  condensation  at  1  pound  steam 
pressure  as  100,  he  found  the  condensation  at  other  pressures  to 
be  represented  by  the  following  figures : 

1  Ib.   pressure 100  1 15  Ibs.  pressure 126 

5  Ibs.  pressure 108  j  20  Ibs.  pressure 134 

10  Ibs.  pressure 118  | 

Extension-surface  radiators. — In  regard  to  what  is  known  as  ex- 
tension-surface radiators,  they  are  generally  made  in  the  flue  form, 
and  numerous  tests  show  they  are  never  as  effective  per  square  foot 
of  actual  surface  as  are  the  radiators  which  have  no  extension  sur- 
face. Profs.  Denton  and  Jacobus  made  some  tests  to  illustrate 
this  point.  They  tested  two  forms  of  extension-surface  flue  ra- 


46  STEAM  HEATING  AND  VENTILATION. 

diators  and  then  planed  off  the  extensions  and  re-tested  them. 
They  found  that  with  one  radiator,  which  had  43  per  cent,  more 
surface  in  the  first  condition  than  in  the  second,  gave  only  about 
17  per  cent,  more  heating  effect.  This,  however,  is  not  exactly  a 
fair  comparison  on  the  grounds  of  extension  surface  alone,  as  the 
radiators  had  a  much  more  effective  proportioning  of  air-space 
design  with  the  extensions  planed  off. 

Surface  of  radiators. — There  are  other  considerations  which 
alter  the  effectiveness  of  a  radiator  besides  the  design  and  setting, 
notably  the  condition  of  the  surface.  Radiators  are  rarely  used 
with  the  natural  iron  surface,  but  are  painted  in  all  possible  ways. 
The  nature  of  the  surface  has  practically  no  effect  on  the  con- 
vected  heat,  but  a  very  decided  effect  on  the  radiant  heat;  but  as 
the  latter  is  generally  less  than  35  per  cent,  of  the  whole,  the 
effect  on  the  total  heat  emitted  is  not  so  marked.  Furthermore, 
usually  only  the  top  and  outside  surface  of  one  side  is  painted  at 
all.  In  general  the  dark  and  lustreless  paints  are  the  most  effect- 
ive, and  may  even  improve  the  heating  power,  while  the  bright 
shiny  metallic  paints  may  reduce  the  effect  quite  decidedly. 

But  few  tests  as  to  the  effect  of  paints  have  been  made.  Prof. 
Carpenter  found  that  two  coats  of  black  asphaltum  increased  the 
total  heating  effect  by  6  per  cent.,  two  coats  of  white  lead  9  per 
cent.,  rough  bronzing  about  6  per  cent.,  while  a  coat  of  glossy 
white  paint  reduced  it  by  10  per  cent.,  although  the  kind  of  ra- 
diator considered  is  not  mentioned.  The  author  found  that  two 
coats  of  ordinary  "radiator  japan  paint"  had  but  little,  if  any, 
effect,  but  in  one  case,  on  a  38-inch  flue  radiator,  three  coats  of 
gold  bronze  reduced  the  heating  power  by  over  12  per  cent.  This 
loss  was  probably  due  partly  to  the  reduction  in  radiant  heat  from 
the  polished  surface  and  also  to  the  fact  that  the  convected  heat 
was  somewhat  reduced  by  the  heavy  coating  of  paint  acting  as  a 
non-conductor.  This  is  doubtless  sometimes  the  effect  with  old 
radiators  which  have  been  painted  several  times. 

Location  of  radiators. — As  before  stated,  the  setting  of  the  ra- 
diator has  a  decided  effect  on  its  heat-giving  power,  and  no  two 
conditions  can  be  considered  exactly  alike  in  this  regard.  For  di- 
rect radiators,  the  best  place  to  set  them  is  unquestionably  under 
a  window.  The  reason  of  this  is  that  the  greatest  leaks  of  cool 
air  from  outside  are  around  the  window  frames  and  the  greatest 
loss  of  heat  by  radiation  is  from  the  glass.  There  is  in  conse- 


STEAM  HEATING  AND  VENTILATION.  47 

quence  a  decided  downward  current  of  cold  air  at  the  window 
which,  if  the  radiator  is  on  the  opposite  side  of  the  room,  rushes 
across  the  floor  and  is  accelerated  by  the  upward  current  of  hot 
air  from  the  radiator.  Such  a  condition  tends  very  decidedly  to 
make  cold  currents  along  the  floor.  If  the  radiator  be  placed 
under  the  window  the  cold  drafts  are  interrupted  and  the  heat 
more  diffused — moreover,  the  upward  current  from  the  radiator, 
the  downward  current  from  the  window  and  the  leakage  drafts, 
all  combine  to  make  a  resultant  draft  of  cold  air  against  the  side 
of  the  radiator  which  lowers  the  temperature  between  the  loops 
and  altogether  tends  to  increase  the  effectiveness  of  the  surfaces 
very  considerably  over  what  would  be  found  in  still  air. 

Direct  radiators  are  often  put  in  recesses  under  windows  and 
low  radiators  are  sometimes  placed  under  window  seats.  Such 
settings,  while  highly  desirable  from  an  aesthetic  consideration,  de- 
cidedly change  the  effectiveness  of  the  radiator  both  by  shutting 
off  the  radiant  heat  and  by  lessening  the  free  convection.  From 
some  rough  experiments  the  author  is  led  to  believe  that  the  or- 
dinary marble  top,  which  is  often  placed  on  radiators,  will  reduce 
the  heating  effect  from  6  to  15  per  cent.,  depending  on  the  size, 
kind  and  height  of  the  radiator;  but  this  is  not  stated  on  the  au- 
thority of  a  careful  comparative  test. 


CHAPTER  IV.— INDIRECT  RADIATORS. 

The  preceding  chapter  comprised  mainly  a  discussion  of  the 
principles  involved  in  the  action  of  radiators  in  giving  out  their 
heat  to  the  air  and  objects  surrounding,  but  was  confined  almost 
entirely  to  direct  radiation.  Many  of.  the  deductions  as  to  the 
relative  value  of  different  kinds  of  surface  may  be  applied  to  indi- 
rect radiators  as  well,  but  a  theoretical  discussion  of  the  latter  re- 
quires some  entirely  different  considerations  from  those  presented 
in  the  last  chapter  on  direct  radiation.  The  indirect  radiator  is. 
located  below  and  outside  of  the  room  to  be  heated;  it  is  enclosed 
by  a  casing,  which  has  an  air  connection  to  the  outside  of  the 
building,  and  a  hot-air  flue  to  the  room  to  be  heated.  In  this  dis- 
cussion it  should  be  stated  that  the  term  indirect  radiation  is  often 
applied  to  radiators  or  heating  coils  which  are  used  in  connection 
with  a  fan  whjch  creates  a  forced  draft.  In  the  author's  opinion 
this  is  a  mistake,  as  the  element  of  forced  draft  involves  still  other 
considerations,  and  such  radiators  are  merely  heating  coils  for 
mechanical  ventilation  and  should  be  discussed  separately  as  such. 
The  indirect  radiator  proper  depends  entirely  upon  the  draft  ac- 
tion of  the  heated  column  of  air  above  it  for  its  ventilating  effect,, 
and  also  for  a  means  of  communicating  its  heat  to  the  room  above. 

Theory  of  indirect  radiator. — The  theory  of  the  indirect  radiator 
may  be  illustrated  by  the  accompanying  Figure  26,  in  which  R  is 
the  radiator  set  in  a  box,  B,  and  provided  with  a  cold-air  connec- 
tion, C,  to  the  outside  air  (generally  having  a  damper,  d),  and  a 
hot-air  duct,  D,  to  the  room  to  be  heated,  with  a  register,  r,  in  the 
floor  or  wall  of  the  room.  Steam  is  supplied  to  the  radiator  by 
the  pipe,  p,  through  the  casing.  The  heat  of  the  radiator  causes 
a  column  of  hot  air  to  rise  through  D,  and  the  current  is  main- 
tained by  the  excess  of  pressure  of  the  column  of  cold  air  outside 
over  that  of  the  column  of  hot  air  in  D.  The  exact  pressure  which 
creates  this  current  is  found  in  the  excess  weight  of  a  column  of 
cold  air  of  height  H  over  that  of  a  column  of  the  same  height 
and  of  the  temperature  of  the  air  in  D. 

This  may  be  calculated  as  follows,  since  the  weight  of  a  cubic 


STEAM  HEATING  AND  VENTILATION.  49 

4 

foot  of  a  gas  of  any  temperature  is  inversely  proportional  to  its. 
absolute  temperature,  which  is  the  temperature  in  degrees  Fahren- 
heit +  460,  or  W  =  c  -h  (t  -f-  460),  where  W  is  the  weight  per  cu- 
"bie  foot,  t  the  temperature  in  degrees  Fahrenheit,  and  c  a  constant, 
different  for  each  gas  and  which,  for  air,  equals  approximately  40.. 
If  t  be  the  temperature  of  the  cold  air  and  T  be  that  of  the  air  in 
D,  then  the  pressure  per  square  foot  due  to  a  column  of  cold  air  of 
height  H  feet  would  be  p  =  40  H  -r-  (t  +  460)  and  the  pressure 


Figure  26.— Diagram  of  Indirect  Apparatus. 

due  to  a  column  of  hot  air  of  the  same  height  would  be  P  = 
40  H  -T-  (T  +  460).  The  difference  of  pressure  which  creates  the 
flow  of  air  then  is 

40  H  40  H  40H(T  — t) 


t  +  460        T  +  460         (t  +  460)  (T  +  460) 
The  head,  h,  which  creates  the  velocity  of  flow,  is  equal  to  the 
height  of  a  column  of  air  of  temperature  T  which  would  give  the 
pressure  p,  or 


h  = 


H(T  — t) 


40  t  +  460 

By  the  laws  governing  the  flow  of  fluids  the  theoretical  velocity 


50  STEAM  HEATING  AND  VENTILATION. 

with  which  the  current  of  air  would  move  through  D  is  v  =  j/  2gh 
where  h  is,  as  above,  the  head  producing  the  flow.  This  would  be 
the  velocity  produced  in  D  by  the  difference  in  pressure  p  were  it 
not  for  the  resistance  to  the  flow  caused  by  the  friction  of  the  air 
in  passing  through  the  radiator  and  ducts  and  past  dampers,  regis- 
ters, etc.  This  resistance  often  reduces  the  velocity  to  less  than 
half  of  the  theoretical  velocity.  Mr.  Alfred  E.  Wolff,  however, 
recommends  that  50  per  cent,  of  the  theoretical  velocity  be  taken 
in  the  case  of  ventilating  flues  which  depend  on  a  heated  column 
for  their  action. 

The  practical  application  of  this  theory  is,  however,  one  of  con- 
siderable difficulty.  In  an  indirect  radiator  in  a  given  situation 
we  do  not  know  the  temperature  of  the  heated  column,  and,  what 
is  most  important,  we  do  not  know  the  resistance  of  the  air  pas- 
sages. What  we  do  know  is  that  we  have  a  radiator  of  so  many 
square  feet  surface  located  in  a  certain  system  of  boxing,  ducts, 
etc.,  and  supplied  with  steam,  or  hot  water,  at  a  certain  tempera- 
ture. The  temperature  of  the  air  outside  being  also  known,  or 
assumed  for  extreme  conditions,  the  question  is  how  much  air  will 
be  delivered  by  this  radiator  to  the  room  and  also  to  what  degree 
it  will  be  heated. 

The  amount  of  heat  given  off  to  the  air  depends  upon  the  ve- 
locity and  upon  the  difference  between  the  temperature  of-  the 
steam  in  the  radiator  and  the  mean  temperature  of  the  air  around 
it;  and  the  velocity  depends,  again,  upon  the  difference  of  tem- 
perature between  the  entering  and  out-going  air  as  well  as  upon 
the  air  resistance  as  embodied  in  the  arrangement  of  ducts,  struc- 
ture of  radiator,  etc.  All  of  these  make  a  complicated  system  of 
variables  which  it  is  impossible  to  apply  in  theoretical  formulas  and 
anticipate  what  the  actual  result  will  be.  In  practice,  a  given  ra- 
diator in  a  given  setting,  and  with  given  temperatures  of  steam  and 
outside  air,  condition  of  wind  being  constant,  will  deliver  a  definite 
amount  of  air  heated  to  a  definite  degree  and  the  velocity  and  final 
temperature  adjust  themselves  until  there  is  an  equality  between 
the  temperature  head  acquired  and  the  velocity  head  plus  the  head 
necessary  to  overcome  the  resistance.  But  exactly  how  this  com- 
bination will  adjust  itself  it  is  wellnigh  impossible  to  say  before- 
hand, inasmuch  as  the  air  resistance  is  a  quantity  very  difficult  tc 
predetermine,  it  being  very  greatly  affected  by  a  slight  change  in 
the  arrangement. 


STEAM  HEATING  AND  VENTILATION. 


51 


Mills'  test  of  indirect  radiators. — For  these  reasons,  all  rules  thus 
far  deduced  for  installing  indirect  radiators  are  entirely  empirical. 
But  very  few  tests  have  been  made  upon  indirect  radiators  with  a 
view  to  establishing  the  relation  between  any  of  the  variables  in- 
volved; but  SQme  valuable  results  might  be  obtained  by  a  thorough 
series  of  experiments  carefully  and  systematically  carried  out.  Mr. 
J.  H.  Mills,  in  his  work  on  Heat,  published  in  1883,  presents  the 
collected  results  of  a  number  of  tests  on  several  indirect  radiators 
of  different  types.  These  tests  were  made  on  various  radiators  at 
various  times  and  by  several  different  experimenters. 

The  writer  has  taken  from  the  Mills  table  the  results  given  for 
the  two  radiators  upon  which  the  greater  number  of  tests  were 
:made  and  has  endeavored  by  plotting  some  diagrams  from  them  to 
determine  something  of  the  relationships  between  the  existing 
variables.  The  results  published  by  Mr.  Mills  on  the  Gold  pin 
radiator  and  the  Whittier  radiator  are  presented  in  the  accom- 

TESTS  ON   GOLD'S  PIN  INDIRECT   RADIATOR. 

Tempera-  Diff.  Temp.^  %       $ 

tures.    . . ,  a  rt      a  t:  OT 


Experimenter. 


C.   B.   Richards....  1873-4 

W.   J.    Baldwin....  1875 

W.  Warner   .......  1880 

Dr.   Gray    .........  1875 

C.  B.  Richards....  1873-4 

J.  R.  Reed  .........  1875 

C.   B.   Richards....  1873-4 

J.  H.   Mills  ........  1876 

W.   J.    Baldwin  ____  1885 

J.  H.   Mills  ........  1876 

W.   J.    Baldwin....  1885 

C.   B.    Richards....  1873-4 

J.   H.  Mills  ........  1876 

J.   H.  Mills  ........  1876 

J.  H.   Mills  ........  1876 

J.   H.  Mills  ........  1876 


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TESTS  ON  G.  WHITTIER'S  INDIRECT  RADIATOR. 


C.   B.   Richards....  1873-4 

J.   R.   Reed 1875 

€.   B.   Richards....  1873-4 

J.  R.  Reed 1875 

J.   R.-  Reed 1875 

C.   B.   Richards....  1873-4 


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6.66  212  416 

5.50  308  344 

5.86  307  366 

8.53  319  533 


C.   B.   Richards....  1873-4  215      0      77      77    215     10.14    428     634 


STEAM  HEATING  AND   VENTILATION. 


panying  table.  In  the  accompanying  diagrams,  Figures  27  and 
28,  the  relation  between  the  British  thermal  units  given  off  per 
hour  per  square  foot  of  radiator  and  the  cubic  feet  of  air  per  square 
foot  of  radiator  per  hour  has  been  plotted  from  these  results. 
This  last  quantity  is,,  of  course,  a  measure  of  velocity  and  is  the 
only  one  which  is  of  practical  value  in  the  comparison  of  different 
radiators.*  The  author  has  -marked  each  of  the  points  on  the 
diagrams  with  the  difference  of  temperature  between  the  steam 
and  the  entering  air.  At  first  inspection  there  seems  to  be  but 
little  uniformity  in  the  arrangement  of  points,  but  a  little  study 
shows  that  for  those  representing  the  same  difference  of  tempera- 
ture the  relation  between  the  heat  units  per  squa-re  foot  and  the 
cubic  feet  of  air  per  square  foot  may  be  represented  by  a  fairly 
uniform  curve. 


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.  s:  A«Air  in  Cub.  Ft. per  Hour  per  Sq.  Ft.  of  Radiation . 

Figure  27.— Tests  of  Gold  Pin  Radiator. 

On  the  diagram  of  the  tests  of  the  Gold  pin  radiator  are  plotted 
the  curves  representing  the  relation  for  a  difference  of  tempera- 
ture of  215  degrees  Fahr.,  and  also  approximately  that  for  a 
difference  of  150  or  160  degrees.  On  the  diagram  for  the  Whit- 
tier  radiator  are  plotted  only  the  curve  for  tests  at  a  difference  of 
temperature  of  215  degrees.  There  are  some  points,  which  are 
marked  by  a  cross  on  the  diagram,  that  seem  to  be  decidedly  out 
of  place;  that  is,  for  the  difference  of  temperature  the  ratio  be- 
tween the  British  thermal  units  per  square  foot  and  the  cubic  feet 
of  air  per  square  foot  is  too  low.  Considering  the  fact,  however, 

*  Mr.  Mills  gives  a  diagram  somewhat  similar  to  these,  but  tue  au- 
thor cannot  find  that  the  points  given  are  taken  directly  from  the  tests 
which  he  produces. 


STEAM  HEATING  AND  VENTILATION. 


53 


that  the  tests  under  discussion  were  made  on  radiators  of  different 
•sizes,  and  several  years  apart,  by  different  men,  and  under  very  dii?- 
ferent  conditions  of  setting,  the  uniformity  of  the  curves  is  very 
striking,  and  the  few  points  which  are  evidently  out  of  place  are 
doubtless  due  either  to  some  error  of  observation  or  in  some 
marked  difference  in  the  way  of  taking  measurements. 

Inasmuch  as  in  practice  we  are  most  concerned  with  extreme 
conditions,  the  curves  for  the  difference  of  temperature  of  215  de- 
grees are  of  most  value,  as  they  may  be  taken  to  represent  an 
initial  air  temperature  of  0  degree  and  low-pressure  steam  at  215 
degrees.  It  will  be  noticed  that  the  215-degree  curve  for  the  Gold 
pin  radiator  is  quite  different  from  that  for  the  Whittier.  As  these 
curves  show  for  a  constant  difference  of  temperature,  the  relation 
between  the  cubic  feet  of  air  per  square  foot  of  radiator,  which 
is  a  measure  of  the  velocity  of  air  flow,  and  the  heat  given  off  per 


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A- Air  in  Cub.  Ft.per  Hour  per  Sq.  Ft  .of  Radiation. 

THE  ENGINEERING  RECORD, 

Figure  28.— Tests  of  Whittier  Indirect  Radiator. 

square  foot,  they  take  into  consideration  all  variations  in  setting; 
and  the  similar  curves  for  any  two  radiators  indicate  precisely  the 
relative  values  of  the  two  radiators.  For  example,  the  215-degree 
curve  of  the  Gold  pin  radiator  shows  a  uniformly  higher  ratio  be- 
tween the  British  thermal  units  per  square  foot  and  the  cubic 
feet  of  air  per  square  foot  than  the  similar  curve  of  the  Whittier. 
The  former  is,  by  just  so  much,  therefore,  the  more  effective  ra- 
diator. Mr.  Mills  states  of  the  Gold  pin  radiator,  which  was  first 
introduced  by  Mr.  Samuel  Gold  in  1862,  that  it  "has  proved  the 
most  efficient  indirect-heating  surface  ever  produced."  It  is  still 
extensively  used,  although  some  modern  makes  are  largely  sup- 
planting it.  It  is  to  be  regretted  tests  have  not  been  made  on  some 
of  the  more  modern  types  in  comparison  with  it. 


54  STEAM  HEATING  AND  VENTILATION. 

If  it  is  desired  to  consider  this  question  mathematically,  the 
equation  of  the  215-degree  curve  of  the  Gold  pin  radiator  is  ap- 
proximately H  =  8.28  A0'79,  whereas  the  equation  of  the  similar 
curve  of  the  Whittier  radiator  is  H  =  11.8  A°k68,  in  which  H  repre- 
sents the  British  thermal  units  per  square  foot  and  A  the  cubic, 
feet  of  air  per  square  foot.  In  other  words,  with  the  Gold  pin 
radiator  the  heat  is  proportional  to  the  79/100  power  of  the  num- 
ber of  cubic  feet  of  air  per  square  foot  of  radiation  (nearly  equal 
to  the  fourth  root  of  the  cube),  while  with  the  Whittier  it  is  pro- 
portional to  the  0.68  power  (nearly  the  cube  root  of  the  square); 
and  the  nearer  this  exponent  approaches  unity  the  more  effective 
will  the  radiator  be,  unless  there  is  a  large  variation  in  the  coeffi- 
cient. 

As  yet  there  is  not  very  much  practical  data  on  indirect  radia- 
tors. It  would  be  of  special  value  if  some  tests  were  made  of  the 
more  modern  forms  of  indirects  to  establish  corresponding  dia- 
grams for  them.  Such  tests  should  be  made  preferably  in  cold 
weather  and  with  a  constant  difference  of  temperature  between 
the  steam  and  entering  air  of  about  215  or  220  degrees.  The 
setting  of  the  radiator  and  air  ducts  should  approximate  practical 
conditions  and  the  velocity  (as  cubic  feet  of  air  per  square  foot  of 
radiator)  could  be  varied  by  changing  the  resistance  to  air  flow 
by  means  of  dampers.  In  this  connection  some  experiments  of 
much  practical  value  could  also  be  made  on  the  air  resistance  by 
determining  the  velocity  in  cubic  feet  of  air  per  square  foot  of 
radiator  attained  for  different  temperatures  in  the  hot-air  duct, 
D,  in  Figure  26. 

Indirect  radiators  are  seldom  installed  except  for  rooms  on  the 
first  or  second  floors;  and  in  the  former  case  the  duct,  D,  is  very 
short,  and  in  the  latter  it  is  usually  from  12  to  16  feet  long.  It 
should  be  stated  in  this  connection  that  indirects  of  large  size 
should  be  spread  out  as  much  as  possible  so  as  to  give  a  large  area 
against  the  current  of  air.  If  they  are  made  of  several  radiators, 
one  above  the  other,  as  is  sometimes  the  case,  by  the  time  the 
air  reaches  the  upper  ones  it  is  of  so  high  a  temperature  that  they 
have  but  little  effect  in  comparison  with  the  lower  section. 

Direct-indirect  radiators. — In  regard  to  direct-indirect  radia- 
tors, their  action  is  much  the  same  as  that  of  the  indirect;  but 
they  have  the  added  effect  of  radiation,  whereas  with  the  indirect 
all  heat  is  conveyed  by  convection.  Furthermore,  with  the  direct- 


STEAM  HEATING  AND  VENTILATION.  53 

indirect  type,  the  flues  are  much  shorter  and  the  air  resistance 
much  less  than  with  the  indirect  setting.  As  a  matter  of  fact,  the 
principal  air  resistance  with  the  former  is  due  to  the  passage  of 
the  air  through  the  radiator  itself. 

The  author  knows  of  no  tests  that  have  been  made  on  direct- 
indirect  radiators,  but  considers  they  would  be  of  value  if  they 
should  establish  the  relation  between  the  heat  given  out  and  the 
air  delivery  per  square  foot  of  radiator  for  constant  differences  of 
temperature  between  the  steam  and  entering  air.  As  stated  in  a 
previous  chapter,  in  the  opinion  of  the  author  the  use  of  the  direct- 
indirect  radiator,  which  has  been,  up  to  this  time,  and  is  now,  very 
limited,  will  be  materially  increased  in  the  immediate  future,  as 
in  connection  with  exhaust  fans  they  form  an  effective  means  of 
introducing  adequate  ventilation  into  buildings  which  are  not  very 
densely  populated  but  in  which  there  is  a  decided  need  of  ventila- 
tion. This  class  of  buildings  includes  especially  our  palatial  mod- 
ern office  buildings  and  also  a  certain  class  of  factories.  The  more 
extensive  introduction  of  these  radiators,  as  well  as  of  the  indi- 
rects,  is  greatly  delayed  by  the  lack  of  accurate  information  as  to 
what  the  different  makes  on  the  market  will  do  in  the  way  of  heat- 
ing under  various  practical  conditions  of  temperature  and  setting. 
There  seems,  therefore,  to  be  a  considerable  field  for  investiga- 
tion in  this  regard. 

Circulation  in  radiators. — In  the  preceding  chapter,  and  thus 
far  in  this  one,  we  have  discussed  the  action  of  radiators  in  doing- 
the  work  they  are  intended  for,  and  have  pointed  out  the  theo- 
retical and  practical  considerations  involved.  Before  discussing 
the  bearing  of  these  principles  upon  the  design  of  a  heating  plant 
it  is  necessary  to  turn  the  attention  to  another  consideration  in- 
volved in  the  action  of  radiators,  and  one  which  is  of  much  im- 
portance in  the  practical  efficiency  of  a  heating  plant.  This  is 
the  circulation  of  steam  within  the  radiator. 

Any  one  who  has  had  even  a  slight  experience  with  radiators 
well  knows  the  troubles  that  arise  on  .account  of  dripping  air 
valves,  water-hammer,  and  the  pocketing  of  air,  and  other  evils 
that  are  due  to  imperfect  steam  circulation.  While  evils  of  this, 
kind  are  frequently  attributable  to  imperfect  circulation  in  the 
piping,  yet  there  is  a  great  difference  in  the  operation  of  radiators, 
in  this  respect. 

As  shown  in  a  previous  chapter,  any  heating  system  contains  a 


UMIWCDQITV     S 


56  STEAM  HEATING  A\'D  VENTILATION. 

considerable  amount  of  air,  and  it  is  necessary  to  provide  means 
for  venting  the  piping  and  radiators  so  as  to  allow  it  to  escape  in 
the  proper  way.  Ordinarily,  when  steam  is  shut  off  from  a  radiator 
it  fills  with  air  at  atmospheric  pressure,  through  the  air  valve; 
and  when  steam  is  turned  on,  this  air  must  in  some  way  be  allowed 
to  escape  before  all  of  the  surface  can'have  full  heating  effect.  The 
rapidity  with  which  the  air  will  be  displaced  by  the  steam  depends 
on  where  the  air  valve  is  placed  and  on  the  design  of  the  radiator. 
In  some  radiators  the  air  will  flow  out  the  air  valve  and  be  fol- 


Water  Line  formed  by  raising  of 
connection. 


I 


Steam    Radiator. 


I 


Hot- Water    Radiator. 

Figure  29. — A  Cause  of  Retarded  Air  Expulsion. 


lowed  up  by  the  steam  rapidly  and  uniformly;  while  in  others  the 
air  will  pocket  in  places,  and  it  may  be  hours  before  it  all  works 
out.  The  action  of  radiators  in  this  regard  is  very  peculiar,  and 
it  is  frequently  exceedingly  difficult  to  predict  beforehand  whether 
or  not  a  radiator  will  allow  good  circulation. 

As  a  general  thing  the  simplest  radiators  are  the  most  ef- 
fective. Air  is  heavier  than  steam  of  the  same  pressure,  but  in  a 
lieating  system  the  air  will  always  find  its  way  to  the  dead  end, 
or  point  where  there  is  no  circulation.  If  a  straight,  vertical  pipe, 
closed  at  the  top,  be  connected  to  a  source  of  steam  supply,  any 
air  in  the  system  will  accumulate  at  its  top.  If  steam  is  turned  on 


STEAM  HEATING  AND  VENTILATION.  57 

an  ordinary  two-column  steam  radiator  which  is  full  of  air  and 
has  a  tight  air  valve,  after  some  moments  the  first  few  loops  will 
become  filled  with  steam  and  perfectly  hot,  the  remaining  loops 
being  full  of  air  and  cold.  If  the  radiator  has  a  two-pipe  connec- 
tion the  air  may  work  out  to  some  extent  through  the  return;  but 
if  it  has  only  a  one-pipe  connection  it  will  remain  in  this  condi- 
tion as  long  as  the  air  valve  is  kept  closed.  If,  however,  the  radia- 
tor be  of  the  hot-water  type — that  is,  it  has  its  loops  connected 
by  openings  through  the  top  as  well  as  at  the  bottom — the  steam 
will  run  along  the  top  of  the  radiator,  and  as  long  as  the  air  valve 
is  closed  it  will  remain  hot  across  the  top  and  the  lower  part  of 
the  loops  will  be  cold,  with  the  possible  exception  of  the  two  end 
ones.  If  now  the  air  valves  be  opened,  the  air  will  flow  uniformly 
from  the  regular  steam  type,  the  steam  filling  one  loop  after  an- 
other; but  with  the  hot-water  type,  as  soon  as  the  air  valve  is 
opened  the  steam  will  flow  first  across  the  top,  then  across  the 
bottom,  and  the  air  will  gradually  work  out,  first  from  the  loops 
near  the  air  valve.  This  will  serve  to  illustrate  to  some  extent  the 
action  of  air  in  radiators. 

Circulation  in  direct  radiators. — As  regards  direct  radiators,  the 
ordinary  two-column  steam  type  gives  the  most  perfect  circula- 
tion. When  steam  is  turned  on  it  compresses  the  air  to  the  press- 
ure of  the  steam,  and  immediately  fills  a  portion  of  the  bottom 
and  the  nearest  loops  to  the  inlet.  Each  loop  then  acts  independ- 
ently and  the  air  syphons  out  of  each,  one  after  another,  until 
all  are  full  of  steam.  In  the  hot-water  type,  as  shown,  the  steam 
has  a  free  circulation  around  the  radiator  as  a  whole,  which  inter- 
feres with  the  air  circulation  in  each  loop,  so  that  these  radiators 
will  often  remain  air  bound  in  the  center  for  a  considerable  length 
of  time.  In  the  same  way  three  and  four-column  radiators  will 
become  air  bound  in  the  middle  columns,  the  air  syphoning  out  of 
the  two  outside  columns  and  establishing  a  circulation  there,  while 
the  contents  of  the  inner  columns  remain  quiet.  In  this  connec- 
tion it  should  be  stated  that  a  strictly  one-column  radiator  would 
not  allow  circulation  at  all,  or  but  very  slowly,  but  the  so-called 
one-column  radiators  are  practically  two  columns,  as  they  are  cast 
with  a  partition  running  up  the  loop  with  an  opening  at  its  top. 
Radiators  of  the  flue  pattern  always  have  one  or  two  similar  parti- 
tions. Direct  radiators  which  are  low  and  wide  are  almost  uni- 
versally built  with  the  loop  opening  in  the  top  as  well  as  the  bot- 


58  STEAM  HEATING  AND  VENTILATION. 

torn,  under  the  impression  that  otherwise  the  outside  portions  of 
the  loops  would  easily  become  air  bound.  Some  of  the  author's 
experiences,  however,  lead  him  to  think  that  as  far  as  this  is  con- 
cerned the  circulation  in  this  type  also  is  better  without  the  top 
connection.  There  is,  however,  one  practical  advantage  which  the 
top-connection  radiators  have  over  the  steam  type,  that  is  more 
especially  marked  in  long,  low  radiators.  If,  with  a  one-pipe  con- 
nection, the  supply  end  is  somewhat  raised,  on  account  of  bad  steam 
fitting,  the  unwarranted  expansion  of  a  riser,  or  other  cause,  it 
may  trap  the  end  loops  of  the  steam  type  so  as  to  shut  off  the  air 
valve  entirely,  whereas  the  top-connection  type  would  have  a  cir- 
culation in  any  such  case,  as  is  illustrated  in  Figure  29.  Such  a 


Figure  30,— Gold's  Pin  Radiator, 


condition,  though  the  result  either  of  poor  design  or  bad  work- 
manship, is  still  a  frequent  occurrence  in  practice. 

Circulation  in  indirect  radiators. — Indirect  radiators,  which  are 
always  made  to  lie  horizontal,  are  usually  made  with  loops  equiva- 
lent to  the  two-column  form,  but  of  greatly  exaggerated  width  and 
very  low,  and  have  the  steam  connection  at  one  of  the  lower  cor- 
ners. There  are,  however,  some  special  forms,  and  one  has  to  use 
his  judgment  as  to  their  qualities  in  respect  to  circulation. 

It  is  important  that  radiators  be  built  and  set  so  that  but  little, 
if  any,  water  will  stand  in  them.  The  openings  for  pipe  connec- 
tions should  be  at  the  lowest  point  and  the  radktor  should  drain 
perfectly.  The  loops  of  some  radiators  are  built  so  that  there  is 
quite  a  pocket  under  the  opening.  This  should  be  avoided,  as  the 


STEAM  HEATING  AND  VENTILATION.  59 

water  which  stands  in  them,  and  is  allowed  to  become  cold,  is  a 
fertile  cause  of  water-hammer  as  well  as  dripping  air  valves.  When 
the  steam  is  turned' into  the  cold  radiator  it  is  apt  to  gather  up 
this  water,  together  with  the  freshly  condensed  water,  and  drive 
it  into  the  back  end,  clogging  up  the  passages  and  causing  water- 
hammer  and  dripping  air  valves,  to  the  great  discomfort  of  those 
in  proximity. 

Air  valves. — In  regard  to  air  valves  there  is  but  little  to  be  said. 
They  are  a  necessity  to  every  radiator;  without  them  any  radiator 
would  soon  become  dead  by  being  filled  with  air.  Automatic  air 
valves  have  almost  entirely  superseded  the  old-time  hand  air 
valves.  They  are  made  with  a  composition  disc,  with  a  high  coeffi- 
cient of  expansion,  which  is  arranged  to  close  the  valve  as  soon 
as  the  hot  steam  comes  in  contact  with  it.  They  are  also  pro- 
vided with  a  screw  attachment  by  which  the  valve  opening  can 
be  adjusted  after  the  valves  are  in  place.  The  disadvantage  of 
the  automatic  air  valve  is  that  when  steam  is  turned  on,  the  entire 
radiator  will  become  heated.  For  this  reason  the  author  prefers 
the  plain  hand  air  valve  on  radiators  in  his  own  rooms,  as  the 
amount  of  the  radiator  heated  can  be  very  accurately  regulated 
by  means  of  them,  especially  when  they  are  connected  on  a  one- 
pipe  system.  The  automatic  air  valve,  however,  takes  the  circu- 
lation in  the  radiator  entirely  out  of  the  hands  of  persons  who 
are  not  acquainted  with  their  principles,  and  in  the  case  of  indi- 
rects  is  a  necessity. 

Air  valves  are  generally  placed  about  18  inches  from  the  bottom 
of  the  last  loop.  Theoretically  the  best  location  would  be  near 
the  bottom  of  this  loop,  but  if  there  is  danger  of  much  water  in 
the  radiator  they  are  safer  near  the  top.  The  author  has  cured 
several  cases  of  a  dripping  air  valve  by  tapping  it  into  the  extreme 
top  of  the  loop.  When  so  placed  the  last  loop  will  sometimes  re- 
main partially  air  bound  on  one  side,  hut  otherwise  they  are  quite 
effective  in  this  position.  The  trouble  referred  to,  however,  is 
much  more  often  due  to  improper  piping  than  to  anything  in  the 
design  of  the  radiator. 


CHAPTER  V.— DESIGN  OF  KADIATION. 

Heat  loss  in  buildings. — There  have  been  considered  in  previous 
chapters  the  various  kinds  of  radiators  in  use  and  the  amount  of 
heat  given  off  by  them  under  different  conditions;  and  the  subject 
now  approaches  a  study  of  the  particular  way  in  which  the  heat  is 
utilized.  The  object  of  any  heating  system  is,  of  course,  to  main- 
tain a  uniform  temperature  in  the  building  in  question,  and  to  do 
this  it  is  necessary:  First,  to  replace  the  heat  lost  by  convection 
and  radiation  from  the  windows  and  walls  of  the  building  to  the 
colder  surroundings  outside;  second,  to  heat  to  the  required  tem- 
perature any  air  that  may  be  intentionally  admitted  for  ventila- 
tion; and  third,  to  heat  also  the  air  that  may  be  admitted  unin- 
tentionally through  cracks  of  window  frames  and  porous  walls  and 
opening  doors.  The  amount  of  heat  required  for  this  last  cause 
is  much  greater  than  is  generally  supposed. 

The  amount  of  air  that  will  pass  through  the  walls  of  an  ap- 
parently tight  room  is  incredible  to  those  who  are  not  familiar 
with  it  by  actual  experiment.  The  author  knows  of  no  experi- 
mental data  on  the  subject,  but  Dr.  John  S.  Billings,  in  his  valua- 
ble work  on  "Ventilation  and  Heating,"  describes  a  simple  and  in- 
teresting experiment  that  may  be  undertaken  by  any  one.  Take 
a  room  of  average  proportions,  heated  by  a  hot-air  furnace  or  in- 
direct radiation,  and  the  air  will,  on  a  fairly  cold  day,  be  coming 
through  the  register  with  a  very  considerable  velocity.  If  now 
this  velocity  be  measured  by  an  anemometer,  or  other  means,  and 
all  doors  and  windows  be  closed  and  the  measure  be  again  taken,  it 
will  generally  be  found  that  there  is  scarcely  an  appreciable  reduc- 
tion in  this  velocity.  If  now  all  the  cracks  of  the  doors  and  win- 
dows be  carefully  stopped  up  with  cloth  or  paper,  the  reduction  in 
the  velocity  of  the  incoming  air  will  still  be  but  very  little  reduced. 
Some  of  the  air  in  such  cases  escapes  directly  through  the  plastered 
and  papered  walls,  but  more  through  floors  and  into  the  outside 
air  through  brick  walls,  between  the  floors,  and  at  such  points  as 
are  not  plastered  and  papered.  In  cold  weather  it  will  generally 


STEAM  HEATING  AND  VENTILATION.  61 

be  noticed  that  with  all  windows  and  doors  closed,  there  is  a  de- 
cided current  of  air  flowing  through  any  building,  in  the  same  di- 
rection as  the  wind  out  of  doors,  and  this  is  always  most  noticeable 
at  the  floors. 

It  may  be  stated  in  general  that  brick  buildings  are  much  tighter 
than  wooden;  and  fireproof  buildings  which  have  wooden  flooring 
laid  on  some  kind  of  a  concrete  filling  are  much  tighter  than  the 
ordinary  brick  buildings.  It  is  perhaps  a  valuable  thing  that  the 
walls  of  buildings  are  not  less  porous  than  they  are,  for  in  far  too 
many  cases  there  is  no  ventilation  in  winter,  except  what  is  ob- 
tained in  this  way.  It  is,  however,  much  better  to  make  the  walls 
tight  and  provide  some  proper  inlet  for  ventilation,  especially  as 
from  a  sanitary  standpoint  the  floor  is  the  worst  place  to  let  cold 
air  into  an  otherwise  warm  room.  An  ordinary  brick  building  can 
be  much  improved  in  this  respect,  if,  during  construction,  the  walls 
around  the  joists  and  for  some  inches  above  and  below  be  painted 
with  a  heavy  coat  of  asphalt  paint.  It  is  for  these  reasons  mainly 
that  all  rules  for  proportioning  radiation  surface  are  very  largely 
empirical. 

The  heat  required  for  a  definite  amount  of  ventilation  can  be 
very  accurately  calculated.  A  cubic  foot  of  ordinary  air,  at  60  or 
TO  degrees  Fahr.,  weighs  about  0.0745  pound,  or  there  are  13.4 
cubic  feet  per  pound;  and  the  specific  heat  is  about  0.24,  so 
that  one  British  thermal  unit  will  heat  55.8  cubic  feet  of  air  1 
degree  Fahr.  This  factor  is,  however,  subject  to  considerable 
variation  according  to  the  final  temperature  considered  and  the 
degree  of  moisture,  and  is  usually  taken  at  55. 

The  heat  lost  by  radiation  and  convection  from  the  walls  of 
buildings  has  been  variously  calculated  by  different  authorities, 
from  Peclet  down,  and  a  great  variety  of  results  have  been  given. 
It  is  unquestionably  very  difficult  to  determine  it  experimentally, 
because  of  the  fact  that  the  loss  of  heat  from  walls,  etc.,  depends 
first  upon  the  construction  of  the  walls,  but  more  especially  upon 
the  condition  of  the  air  outside,  the  loss  of  heat  being  very  greatly 
increased  by  a  slight  wind  blowing  against  the  exposed  surface. 
The  loss  of  heat  is  greatest  from  the  glass  surface  of  windows. 
Mr.  W.  J.  Baldwin,  in  his  book  on  "Steam  Heating  for  Buildings," 
which  has  for  some  years  been  a  standard,  publishes  a  table  of  the 
relative  "heat-transmitting  power  of  various  building  substances/* 
which  is  given  here. 


62  STEAM  HEATINU  AND  VENTILATION. 

BALDWIN'S  TABLE  OF  HEAT-TRANSMITTING  POWER  OF  BUILDING 

SUBSTANCES. 

Window  glass  1,000 

Hardwood  sheathing  on  walls 66  to  100 

White  pine  and  pitch  pine 80  to  100 

Lath  and  plaster,  good 75  to  100 

common   100  to  150 

Common  brick,  rough 150 

hard  finish  200 

hollow  walls,  hard  finish 150 

Sheet  iron  1,100  to  1,200 

Mr.  Baldwin  further  implies  that  the  coefficient  representing 
the  amount  of  heat  given  off  by  glass  surface  per  square  foot  per 
hour  per  degree  difference  in  temperature  between  one  side  of  the 
glass  and  the  other  is  about  the  same  as  the  similar  coefficient  for 
radiation,  which  may  be  taken  at  about  1.8  British  thermal  units. 

The  German  Government  made  an  investigation  into  this  sub- 
ject, and  the  results  of  its  work  have  been  translated  into  English 
measures  by  Mr.  Alfred  E.  Wolff  (Journal  Franklin  Institute,  Vol. 
134);  and  Prof.  R.  C.  Carpenter  has  translated  the  results  of 
Peclet's  original  investigations.  The  factors  given  differ  very  de- 
cidedly, as  may  be  seen  by  the  accompanying  table,  in  which  are 
given  the  coefficients  of  heat  transmission  for  different  surfaces : 

TABLE  OF  COEFFICIENTS  OF  HEAT  TRANSMISSION. 

(British  thermal  units  transmitted  per  hour  per  square  foot  of  sur- 
face per  degree  difference  of  temperature.) 

Peclet.      German  Gov. 
Baldwin.  (Carpenter.)         (Wolff.) 

Single  skylight  ..  1.12 

Double  skylight    ..  0.62 

Single   window    1.8  .91  to  .98  1.03 

Double    window    .60  to  .66  .52 

4-inch  brick  wall.    )  (  .27  .43  .68' 

S-inch  brick  wall.«  [  -{to  .27  .46 

13-inch  brick  wall.  )  (  .36  .32  .32 

17-inch  brick  wall .26  .24 

Wooden  beams  planked  over  as  flooring 0.083 

Wooden  beams  planked  over  as  ceiling 0.104 

Fireproof  construction  as  flooring 124 

Fireproof  construction   as   ceiling 145 

Wooden  door 414 

Mr.  John  J.  Hogan  gives  1.57  British  thermal  units  as  the  co- 
efficient for  glass.  Mr.  Charles  Hood,  the  English  authority, 
states  that  one  square  foot  of  glass  will  cool  1.279  cubic  feet  of 
air  one  degree  per  minute  per  degree  difference  in  temperature. 
This  is  equivalent  to  a  coefficient  of  heat  transmission  of  about 
1.40  British  thermal  units  per  hour.  Mr.  Hood  adds  that  this  was 
determined  in  still  air  and  that  it  is  very  greatly  increased  by  the 


STEAM  HEATING  AND  VENTILATION.  63 

effect  of  wind.  He  states,  however,  that  it  is  well  known  that  in 
extremely  cold  weather  there  is  invariably  but  little  wind,  so  that 
he  considers  this  a  safe  coefficient  to  use. 

Mr.  Wolff  has  constructed  a  diagram  of  heat  transmission  from 
buildings,  which  embodies  the  German  coefficients  with  some  slight 
modifications  based  on  his  own  very  extended  practice.  He  states 
that  he  has  used  this  diagram  in  the  calculations  of  heating  sur- 
face for  buildings,  during  the  past  six  years,  with  the  most  satis- 
factory results.  This  is  a  valuable  recommendation,  and  the 
author  takes  much  satisfaction  in  presenting  the  diagram  here- 
with. 

In  using  his  diagram  for  proportioning  radiation  surface,  Mr. 
Wolff  calculates  by  it  the  number  of  heat  units  lost  from  the  ex- 
posed wall  and  glass  surfaces  and  further  makes  allowance  for  the 
direction  of  winds  on  the  outside  exposure,  as  shown  on  the  small 
diagram  on  page  65  facing  the  main  one.  As  indicated  5  to  25 
per  cent,  is  added  to  the  calculated  amount  of  heat  dissipated  in 
transmission  through  the  actual  wall  surface  and  10  per  cent,  for 
reheating  the  air  constantly  leaking  in.  An  allowance  is  also  ad- 
vised, to  the  amount  of  10  per  cent.,  for  the  transmission  of  heat 
through  floors,  ceilings,  etc.  Where  the  rooms  are  not  large,  one 
calculation  is  made  for  all  these  factors  by  adding  to  the  heat 
transmission  as  obtained  by  means  of  the  main  diagram,  the  per- 
centage given  in  the  small  circle. 

For  "wooden  floors"  in  cheaply  constructed  buildings,  the  author 
would  recommend  even  more  allowance  than  Mr.  Wolff  gives,  since 
where  such  floors  are  used  a  great  loss  of  heat  comes  from  a  large 
amount  of  cold  air,  which,  even  with  a  light  wind  blowing,  will 
work  through  the  brick  walls  where  the  joists  are  set  in  and  where 
the  walls  are  unsealed  by  lathing  or  plaster,  and  find  its  way  into 
the  rooms.  This  is  a  common  source  of  heat  loss  in  cheaply  con- 
structed brick  houses  and  apartment  buildings,  and  is  the  usual 
cause  of  the  cold  floors  which  are  noticeable  in  many  buildings  in 
cold  weather.  In  fireproof  structures,  on  the  contrary,  the  con- 
struction of  the  walls  and  floors  is  much  more  substantial  and 
offers  but  little  opportunity  for  air  to  blow  in  between  the  floor 
and  ceiling. 

Baldwin's  rule  for  direct  radiation. — The  wide  variation  in  these 
coefficients  of  heat  transmission  have  led  to  a  corresponding  varia- 
tion in  the  rules  laid  down  for  proportioning  radiating  surface. 


64 


STEAM  HEATING  AND  VENTILATION. 


100 


90 


80 


o 

X 

k 


60 


£  50 


L 

O- 


30 


© 


10         20         30        40         50         60        7Q        80        50        JOO 
Difference  in  Temperature.  (  De9rees  FahrenVieii.) 
Alfred  R.  Wolff's  Diagram  of  Transmission  of  Heat  in  Buildings. 

A,  vault  light;  E,  single  window;  C,  single  skylight;  D,  4-inch  brick  wall; 
E,  double  window;  F,  double  skylight;  G,  8-inch  brick  wall;  H,  1-inch  pine 
board  door;  I,  12-inch  brick  wall;  J,  concrete  floor  on  earth;  K,  fireproof  par- 
tition; L,  2-inch  pine  board— heavy  door;  M.  16-inch  brick  wall;  N,  20-inch 
brick  wall;  O,  concrete  floor  on  brick  arch;  P,  24-inch  brick  wall;  Q,  28-inch 
brick  wall;  R,  32-inch  brick  wall;  S,  wood  floor  on  brick  arch;  T,  36-inch  brick 
wall;  U,  40-inch  brick  wall;  V,  wood  floor,  double. 


STEAM  HEATING  AND  VENTILATION. 


65 


25 
25     10 


10 


25 
10    15 


In  the  early  days  of  steam  heating,  radiating  surface  was  generally 
figured  by  various  rule-of-thumb  methods,  based  chiefly  upon  the 
cubic  contents  of  the  room  to  be  heated.  These  varied  all  the  way 
from  one  square  foot  of  radiation  for  30  cubic  feet  of  space,  up  to 
one  square  foot  to  100  cubic  feet,  according  to  the  building  con- 
sidered. Mr.  Baldwin,  in  the  earlier  editions  of  the  work  men- 
tioned, gives  a  rule  which  only  takes  into  account  the  exposed  sur- 
face of  the  building.  According  to  this  rule  it  is  first  necessary 
to  figure  what  may  be  called  the  "glass  equivalent  surface/'  This 
is  the  actual  glass  surface  in  a  room  added  to  the  wall  surface  re- 
duced to  its  equivalent  in  glass.  Mr.  Baldwin  refers  to  his  table 
of  relative  heat  transmitting  powers,  previously  given,  and  his  rule 
is  as  follows: 

"In  figuring  wall  surface,  etc.,  multiply  the  superficial  [exposed] 
area  of  the  wall  in  square  feet  by  the  number  opposite  to  the  sub- 
stance in  the  table,  and  divide  by  1,000  (the  value  of  glass),  the 
product  is  the  equivalent  of  so  many  square  feet  of  glass  in  cooling 

power,  and  may  be  added  to  the  win- 
dow surface."  Mr.  Baldwin  then  gives 
a  rule  for  finding  the  number  of  square 
feet  of  radiating  surface  for  each 
square  foot  of  glass,  or  the  equivalent 
of  other  building  substances  in  glass, 
which  may  be  expressed  by  the  follow- 
ing formula : 

K  =  (t  —  ^-r-CT  —  t)XE 
where  t  is  the  required  temperature- 
of  the  room,  ^is  the  temperature  of 

the  outside  air,  T  the  temperature  of  steam  in  the  radiator,  R  the 
radiation  surface,  and  E,  the  glass  equivalent  surface. 

With  an  outside  temperature  of  —  5  degrees,  an  inside  tempera- 
ture of  70  and  steam  at  temperature  of  220,  this  formula  would 
allow  \  square  foot  of  radiating  surface  for  each  square  foot  of 
glass  or  its  equivalent.  Mr.  Baldwin  further  adds:  {ilt  must  be-, 
distinctly  understood  that  [this]  .  '.  .  offsets  only  the  .win- 
dows and  other  cooling  surfaces  it  is  figured  against  and  does  not 
provide  for  cold  air  admitted  around  loose  windows,  or  [through 
walls]  of  poorly  constructed  .  .  .  houses.  These  latter  con- 
ditions, when  they  exist,  must  be  provided  for  separately,  and 
usually  require  as  much  as  50  per  cent,  additional;  a  good  com- 


2?    10 


Floor 
or  Roof. 
10 
10   6& 


5  6A 


10      15 


10     15 


5    (2C 


Exposure  Diagram. 


66  STEAM  HEATING  AND  VENTILATION. 

mon  rule  for  ordinary  purposes  being  three-fourths  of  a  square 
foot  of  heating  surface  to  each  square  foot  of  glass,  or  its  equiva- 
lent." He  further  states  that  he  has  used  this  rule  in  preference 
to  any  other  for  several  years  and  found  it  very  satisfactory.  Fol- 
lowing in  Mr.  Baldwin's  footsteps,  the  writer  has  used  this  method 
of  calculating  surface  in  the  design  of  a  large  number  of  heating 
systems,  chiefly  for  large  office  buildings  in  Chicago  and  else- 
where. He  has  found,  however,  for  low-pressure  systems  in  office 
buildings  that  from  60  to  70  per  cent,  of  the  glass-equivalent  sur- 
face in  figuring  radiation  gives  ample  and  satisfactory  results. 
For  such  buildings  he  has  counted  each  square  foot  of  wall  sur- 
face as  being  equivalent  to  one-tenth  of  a  square  foot  of  glass. 
For  brick  houses  or  apartment  buildings  of  ordinary  construction 
it  is  better  to  take  the  wall  surface  as  15  or  20  per  cent,  of  the 
glass.  For  office  buildings  65  per  cent,  of  the  glass-equivalent 
surface  in  radiating  surface  is  ample  in  most  cases,  and  it  may 
average  rather  less.  It  should  be  greatest  on  the  sides  of  the 
building  which  are  exposed  to  the  severest  winds  in  winter,  and 
.may  be  less  on  the  southern  exposures. 

Mills'  rule  for  direct  radiation. — Mr.  Baldwin's  method  of  calcu- 
lating radiation  surface  calls  for  the  exercise  of  careful  judgment 
on  the  part  of  engineers  using  his  rule,  and  many  authorities  have 
•devised  rules  which  are  more  specific.  Most  of  these  take  into 
raccount  the  glass  surface,  the  wall  surface,  and  also  the  cubic  con- 
tents of  the  room.  The  rule  recommended  by  Mr.  Mills  in  his 
work  is 

E  =  0.50  G  +  0.05  W  +  0.005  C 

in  which  E  is  the  number  of  square  feet  of  radiating  surface;  G, 
the  square  feet  of  glass  surface;  W,  the  square  feet  of  wall  sur- 
face (exclusive  of  windows);  and  C,  the  contents  in  cubic  feet. 
This  rule  is  recommended  where  the  rooms  are  to  be  heated  to  a 
temperature  of  70  degrees  with  an  outside  temperature  of  —  10  to 
—  15  degrees  Fahr.  If  the  outside  temperature  is  less  or  great- 
er, the  result  should  be  multiplied  by  the  proportionate  fac- 
tor. This  is  a  very  good  rule  and  perfectly  safe.  The  writer 
knows  of  a  contractor  who  has  had  a  very  wide  experience  in 
steam  heating  who  uses  this  rule  universally,  except  that  he  mul- 
tiplies the  cubic  contents  by  0.004. 

Willetfs  rule  for  direct  radiation. — Mr.  Jas.  E.  Willett,  an  archi- 
tect of  wide  experience,  who  has  given  much  study  to  heating 


STEAM  HEATING  AND  VENTILATION.  67 

and  ventilation,  formulated,  several  years  ago,  a  very  valuable  rule 
for  proportioning  direct  radiation,  which  is  expressed  by  the  fol- 
lowing formula : 

R  —  o.9  (t  —  tj  (0.60  G  +  0.10  W  +  0.0025  C)  FJ  -M 
where  F  is  a  factor  depending  on  the  method  of  heating  (0.8  for 
low-pressure  steam)  and  J,  a  factor  depending  on  the  exposure, 
which  Mr.  Willetts  puts  as  1.0  for  ordinary  south  and  east  ex- 
posures and  1.4  for  north  and  west.  The  other  letters  in  the 
formula  have  the  same  reference  as  in  the  formulas  previously 
given,  but  Mr.  Willett  states  that  t±  should  be  taken  10  degrees 
higher  than  the  lowest  recorded  temperature  of  the  locality  in 
question.  With  tt  taken  at  minus  8  degrees;  t,  70  degrees;  F,  0.8; 
and  J,  1,  Mr.  Willett's  formula  becomes : 

E  =  0.48  G  +  0.08  W  +  0.002  C. 

This  equation  compares  very  closely  with  Mills,  though  less  al- 
lowance is  made  for  the  cubic  contents  and  more  for  the  wall  sur- 
face. The  writer  considers  that  if  J,  in  Mr.  Willett's  formula,  be 
taken  as  1.  for  south  and  east  exposures,  it  is  sufficient  in  most 
cases  to  take  it  as  1.2  for  north  exposures.  For  such  exposures, 
therefore,  the  same  formula  can  be  used  as  for  south  and  east 
rooms  and  the  radiation  increased  one-fifth. 

Carpenter's  rule  for  direct  radiation. — Prof.  Carpenter,  in  his 
work  on  heating  and  ventilation,  has  devised  a  formula  which  is 
very  carefully  derived.  He  first  calculates  the  amount  of  heat 
lost  from  the  room  in  question  and  then  the  amount  of  radiating 
surface  necessary  to  offset  this  heat,  using  coefficients  for  heat 
transmission  which  he  substitutes  in  his  formula.  According  to 
Prof.  Carpenter's  method,  the  heat  in  British  thermal  units  lost 
from  a  room  for  every  degree  difference  in  temperature  between 
the  inside  and  outside  air  is  h  =  nC  -f-  55  +  G  +  (W-i-4),in  which 
G,  C,  and  W  represent  the  quantities  previously  assigned  them,  and 
n  is  the  number  of  times  the  air  of  the  room  is  to  be  changed  per 
hour.  Prof.  Carpenter  states  that  for  direct  radiation  it  is  neces- 
sary to  take  n  =  2  for  ground-floor  rooms  and  n  =  1  for  others, 
to  allow  for  leakage  of  air.  The  quantity,  nC  -=-  55  gives  the  num- 
ber of  heat  units  necessary  to  raise  nC  cubic  feet  of  air  1  degree 
in  temperature.  Prof.  Carpenter  states  that  the  radiating  sur- 
fact  should  be  equal  to  R  =  [  (t  —  tj  •*•  (T  —  t)  a  ]  h  in  which 
t  is  the  required  temperature  of  the  room,  t±  the  outside  tem- 
perature, T  the  temperature  of  the  steam  in  the  radiator,  and  a 


68  STEAM  HEATING  AND  VENTILATION. 

is  a  coefficient  of  heat  transmission  from  a  radiator  which  varies 
from  1.7  for  low-pressure  steam  heating  to  1.9  for  steam  pressure 
of  40  pounds  and  2.4  for  steam  pressure  of  100  pounds.  Taking 
the  usual  conditions  of  t  =  70  degrees  and  tt  =  —  10  degrees  and 
with  low-pressure  steam  heating,  the  factor,  (t  —  ta)  -=-  (T  —  t)  a 
becomes  0.324,  so  that  with  n  =  I  the  equation  for  radiation  sur- 
face becomes: 

R  —  0.324  G  +  0.08  W  +  0.006  C. 

This  formula  differs  very  considerably,  in  the  factors  used,  from 
those  already  cited,  and  it  will  be  seen  that  it  is  based  upon  the 
coefficient  of  heat  transmission  for  glass  of  1  British  thermal 
unit  per  square  foot  per  degree  difference  in  temperature,  and  the 
radiation  surface  due  to^the  glass  area  is  consequently  much  less 
than  in  the  other  formulas.  The  difference  is  more  than  made  up, 
however,  by  the  larger  allowance  for  the  cubic  contents.  In  the 
opinion  of  the  author,  Prof.  Carpenter's  coefficient  for  glass  is  con- 
siderably too  small,  and  his  equation  gives  results  which  are  too 
large  for  rooms  having  large  cubic  contents  with  comparatively 
small  window  surface,  and  results  which  are  too  small  when  the 
proportions  are  reversed. 

Monroe's  rule  for  direct  radiation.  — The  author  has  recently  de- 
duced a  formula  which  is  a  combination  of  Willett's  and  Carpen- 
ter's, and  is  as  follows: 

R  =  (1.3  G  +  0.25  W  +  0.008  C)  J  (t  —  tx)  -4-  (T  —  t)  a. 
In  this  the  letters  stand  for  the  quantities  previously  assigned,  J 
being  a  coefficient  depending  upon  the  exposure  (being  unity  in 
ordinary  cases)  and  for  the  usual  conditions  as  assumed  in  previous- 
cases,  this  formula  becomes 

R  =  0.42  G  +  0.08  W  +  0.0026  C. 

In  the  following  table  are  given  the  proportions  of  four  repre- 
sentative rooms  of  an  office  building  for  which  the  writer  was  en- 
Radiation  Surface  by 

®  S  T3 

d  1  I    I    I   I  11 

Q,  n-rcrn  z2  a  "-«      r:  *-> 

o          & 
8         H 

1.  West  ,.., 

2.  N.   &  W..    118 
3    N1^     &   E. 

4.  NE. 


u 

W 

u 

a 

g 

d 

S_j 
0 

3 

*  m 

s 

p 

Q 

§ 

PH  ~ 

59 

160 

3360 

54.5 

47 

51 

44 

49 

46 

.18 

312 

2150 

85 

86 

76 

81 

97 

84 

8.5 

420 

4070 

85 

84 

87 

82 

85 

80 

59 

129 

1730 

44.5 

42.5 

40 

46 

47 

40 

STEAM  HEATING  AND  VENTILATION.  69 

gaged  to  design  the  heating  system,  and  for  which  the  heating 
surface  has  been  figured  out  according  to  Mills',  Willett's,  Carpen- 
ter's and  the  author's  formulas,  and  also  according  to  Mr.  Bald- 
win's formula  taking  65  per  cent,  of  the  glass  equivalent  surface. 

The  table  also  gives  the  amount  of  surface  which  was  installed  in 
.each  of  the  four  rooms,  and  which  has  given  perfect  satisfaction 
throughout  two  or  three  severe  winters.  The  radiator  used  was 
the  two-column  cast-iron  radiator,  32  inches  high,  except  in  room 
2,  which  had  a  26-inch  flue  radiator.  The  radiation  in  room  2  was 
made  slightly  less  than  the  amount  calculated,  because  a  large  por- 
tion of  the  wall  surface  was  a  25-inch  brick  wall,  for  which  tho 
multiplier  for  W  might  be  taken  about  0.15  instead  of  0.25. 

It  might  be  stated  that  in  using  the  formula  given,  il  is  to  be 
taken  10  degrees  above  the  lowest  recorded  temperature,  and  the 
factor,  J,  should  be  taken  from  1.05  to  1.15  for  severe  exposures, 
and  may  also  be  increased  0.1  for  ordinary  brick  buildings  with 
wooden  floor  joists,  and  0.2  for  wooden  buildings.  The  factor  a  is 
to  be  taken  at  1.7  for  ordinary  conditions  of  exhaust-steam  heat- 
ing. It  may  be  increased  somewhat  for  heating  at  higher  press- 
ures and  for  buildings  with  low-pressure  heating  and  no  power,  in 
which  steam  pressure  of  10  or  15  pounds  may  be  carried,  it  may  be 
made  equal  to  1.8.  In  such  cases,  also,  the  temperature,  T,  may 
T^e  taken  at  235  degrees.  The  factor  a  should  be  decreased  where 
the  radiators  are  of  an  unfavorable  pattern  or  are  unfavorably  lo- 
cated, according  to  their  relative  heat-giving  power,  under  such 
conditions  as  has  been  pointed  out  in  Chapter  III.  The  last  part 
of  the  formula  need  be  calculated  but  once  for  each  building.  The 
factor  a  may  be  taken  as  high  as  2.8  in  some  greenhouses  and  in 
some  factories  in  which  wrought-iron  pipe  coils  are  used,  which 
are  quite  an  effective  type  of  surface.  Unless  the  coils  are  espe- 
cially favorably  located,  however,  the  factor  should  be  somewhat 
less  than  2.8. 

In  the  general  application  of  the  formula  given  above  it  will  be 
noted  that  the  expression  (t  —  tx)  (1.3  G  +  0.25  W  +  0.008  C)  rep- 
resents the  total  heat  given  off  by  the  room,  and  it  is  equal  to 
K  (T  —  t)  a,  which  is  the  heat  given  off  by  the  radiation  surface. 

Mr.  Wolff  in  his  practice  calculates  the  heat  lost  per  hour  from 
each  room  according  to  his  diagrams  previously  given,  with  the 
allowance  for  exposure  as  shown  thereon.  He  then  (divides  this 
amount  by  the  number  of  British  thermal  units  given  off  per 


70  STEAM  HEATING  AND  VENTILATION. 

square  foot  of  radiator  per  hour,  which  he  takes  as  250  for  a  two- 
column  radiator  (bronzed)  set  under  the  window,  but  this  factor 
varies  within  wide  limits,  as  before  described,  according  to  the 
kind  of  surface  used  and  the  nature  of  the  setting. 

Indirect  radiation. — With  indirect  radiation  the  heat  lost  from 
the  glass  and  wall  surface  must  be  made  up  by  the  heated  air  com- 
ing in  from  the  indirect  radiator,  and  to  accomplish  this  the  en- 
tering air  must,  in  cold  weather,  have  a  temperature  considerably 
above  the  mean  temperature  desired  in  the  room.  The  total  heat 
lost  by  the  room  is  (t — tt)'  h  where  h  is  the  expression  (1.3  G-f- 
0.25  W  +  0.008  C)  and  the  volume  of  air  required  in  cubic  feet  per 
hour  is  V=  (t  —  1 1 )  h  X  58  -=-  (T  —  t)  where  T  is  the  temperature 
of  the  air  leaving  the  radiator.  Now  it  is  necessary  for  the  in- 
direct radiator  to  heat  all  of  this  air  from  the  outside  temperature 
to  the  temperature  T,  and  the  total  heat  required  to  be  given  off 
by  the  radiator  is 

U  =  V(T  —  ^^58  =  ^  —  tOCT  —  yh-r-CT  —  t). 

It  will  be  seen  that  both  U  and  V  vary  rapidly  with  a  change  in 
T,  decreasing  as  T  is  increased.  If  t  —  70  degrees  and  tj  =  — 10 
degrees  for  extreme  conditions,  and  if  T  =  150,  V  will  be  one-half 
and  U  two-thirds  of  what  they  would  be  if  T  were  taken  at  110. 
It  is  this  fact  that  makes  the  indirect  radiator  quite  a  flexible  de- 
vice, for  in  extreme  weather  it  is  possible,  by  partially  shutting  off 
the  air  supply,  to  maintain  easily  the  required  inside  temperature 
at  the  sacrifice  of  a  small  amount  of  ventilation.  If  T  =  120, 
U=:20Sh,  and  V  =  93h;  and  with  T  —  130,  U  =  18G  h,  and 
V  =  77  h.  As  a  rule,  it  is  safe  to  assume  from  450  to  500  British 
thermal  units  per  hour  per  square  foot  of  surface  for  an  indirect 
radiator,  as  will  be  seen  by  reference  to  the  tests  as  described  in 
the  last  chapter,  and  taking  the  former  figure,  with  T  =  120,  E  = 
0.46  h,  and  with  T  =  130,  E  =  0.415  h. 

Inasmuch  as  it  has  been  found  that  for  the  same  conditions  of 
inside  and  outside  temperatures  E  for  direct  radiation  =  0.325  h, 
it  will  be  seen  that  according  to  this  calculation  from  28  to  40  per 
cent,  more  heating  surface  is  required  for  indirect  heating  than 
for  direct.  The  author  has  in  his  practice  used  these  proportions 
for  indirect  radiators,  usually  installing  about  30  per  cent,  more 
than  for  direct;  although  in  some  cases,  where  an  exceptional  de- 
gree of  ventilation  is  desired  and  the  room  has  a  comparatively 


STEAM  HEATING  AND  VENTILATION.  71 

large  amount  of  glass  surface,  more  radiating  surface  is  neces- 
sary. In  such  cases,  and  especially  where  a  large  amount  of  ven- 
tilation is  desired,  it  is  necessary  to  see  that  the  quantity  V,  tis 
obtained  above,  is  equal  to  the  amount  of  air  required  for  ven- 
tilation. It  will  be  found  sufficient  in  all  ordinary  cases  to  change 
the  air  four  times  per  hour,  which  is  generally  satisfactory  for 
private  houses;  but  where  much  entertaining  is  to  be  allowed  for, 
six  times  per  hour  is  better.  In  designing  indirect  radiators  it  is 
necessary  to  be  very  careful  in  the  proportion  of  flues,  but  such 
details  of  construction  will  be  considered  in  the  next  chapter. 

In  proportioning  direct-indirect  radiators  the  same  rules  apply 
as  for  the  indirect  type,  although  their  action  as  direct  radiators 
may  be  counted  on  to  some  extent.  Where  this  kind  of  radiator 
is  used  in  connection  with  an  exhaust  ventilating  system  very  good 
results  are  obtained  by  using  the  author's  formula  for  direct  ra- 
diators, with  an  addition  to  the  0.008  C  of  2/3  K  -f-  55,  where 
K  is  the  cubic  feet  of  air  per  hour  required  for  ventilation.  This 
gives  additional  surface  necessary  to  heat  2/3  K  cubic  feet  of  air 
from  the  outside  temperature  to  that  of  the  room.  The  author 
figures  on  2/3  K  (in  some  cases  f ),  as  in  extreme  weather  the  de- 
gree of  ventilation  may  be  somewhat  reduced.  For  these  ra- 
diators also,  the  factor  a  in  the  formula  may  be  taken  as  1.9  or  2. 


CHAPTER  VI.— PIPING  AND  CONSTRUCTION  DETAILS. 

Having  selected  the  system  of  heating  to  be  employed  accord- 
ing to  the  needs  of  the  building  in  hand,  and  having  proportioned 
the  radiator  surface  according  to  the  requirements  of  the  various 
rooms,  it  then  remains  to  lay  out  the  system  of  piping  and  arrange 
the  various  details  of  construction. 

In  regard  to  piping  connections,  it  should  be  stated  at  the  out- 
set that  the  flow  of  steam  through  any  system  of  piping  depends 
primarily  upon  the  difference  in  pressure  between  that  at  the  sup- 
ply end  and  that  at  the  delivery  or  return  end,  and  without  any 
difference  of  pressure  no  flow  of  steam  can  exist.  In  exhaust  heat- 
ing or  low-pressure  gravity  systems,  this  difference  of  pressure  is 
very  slight,  and  consequently  for  such  systems  the  pipes  have  to  be 
larger  than  for  high-pressure  heating  or  vacuum  systems  in  which 
the  pressure  in  the  returns  is  reduced  by  connecting  them  to  a 
vacuum  pump.  Again,  in  most  systems  of  steam  heating  there  is 
another  consideration  which  affects  the  sizes  of  pipes ;  that  is, 
the  water  of  condensation  from  the  radiators.  If  the  steam  cir- 
culation were  uniform  and  continuous  and  the  water  of  condensa- 
tion kept  separate  from  the  steam  supply,  as  in  properly  arranged 
two-pipe  systems,  the  pipes  might  be  very  small;  but  it  is  neces- 
sary to  allow  for  sudden  opening  of  radiator  valves,  so  as  to  take 
care  of  the  momentary  demand  for  steam  which  this  causes,  as 
well  as  the  rush  of  water  of  condensation  which  accompanies  it. 
For  exhaust  and  low-pressure  gravity  systems,  it  may  be  laid  down 
as  a  general  rule  that  pipe  sizes  should  be  larger  for  the 'simple 
one-pipe  system  than  for  any  other  arrangement.  They  may  be 
smaller  for  the  one-pipe  overhead,  or  Mills  system,  and  still  smaller 
for  the  two-pipe  systems.  A  description  of  various  systems  of 
steam  distribution  was  given  in  Chapter  II. 

Baldwin's  rule  for  pipe  sizes. — In  the  early  days  of  steam  heat- 
ing, pipe  sizes  were  proportioned  by  various  empirical  rules,  the 
usual  basis  of  which  was  the  principle  of  being  sure  to  get  the 
pipes  large  enough;  and  such  rules  are,  to  a  large  extent,  blindly 
followed  to-day.  Mr.  William  J.  Baldwin,  in  his  earlier  work  on 


STEAM  HEATING  AND   VENTILATION.  73 

steam  heating,  gave  a  rule  for  proportioning  steam  pipes  which  is 
very  convenient  and  has  been  very  widely  used.  This  rule  states 
that  in  the  sectional  area  of  the  pipe  there  should  be  allowed  the 
area  of  a  1-inch  pipe  for  every  100  square  feet  of  radiator  surface. 
Inasmuch  as  the  areas  of  circles  are  proportional  to  the  square  of 
their  diameters,  this  means  a  1-inch  pipe  for  100  square  feet,  2- 
inch  pipe  for  400  square  feet,  3-inch  pipe  for  900  square  feet,  8- 
inch  pipe  for  6,400  square  feet,  etc.  These  sizes  are  none  too 
large  for  many  cases,  although  in  plants  with  the  system  care- 
fully arranged  so  that  the  circulation  is  all  in  one  direction  and 
the  water  of  condensation  does  not  have  to  flow  back  against  the 
•current  of  steam,  pipes  can  be  very  considerably  decreased  below 
the  sizes  given  by  this  rule.  Mr.  Baldwin  also  gives  a  diagram  of 
minimum  sizes  for  short  horizontal  supply  mains  from  which  few 
branches  are  taken,  which  give  sizes  very  much  smaller  than  the 
rule  above  quoted.  [See  Table  I.] 

Mills'  rule  for  pipe  sizes. — Mr.  J.  H.  Mills  gives  a  diagram  for 
the  sizes  of  mains  for  one-pipe  overhead  system?  of  which  he  is  the 
originator.  This  diagram  gives  sizes  somewhat  smaller  than  those 
obtained  by  Mr.  Baldwin's  rule.  In  the  accompanying  table  are 
given  the  maximum  square  feet  of  radiation  on  pipes  of  each  size 
according  to  the  rules  of  Baldwin  and  Mills,  as  well  as  Mr.  Bald- 
win's sizes  for  return  pipes.  In  regard  to  his  figures  for  minimum 
sizes  for  mains,  Mr.  Baldwin  states  that  they  represent  minimum 
•conditions  for  lengths  of  50  feet  or  thereabout,  but  that  for  large 
buildings  one  size  larger  should  be  used. 

Monroe's  rule  for  pipe  sizes. — In  his  own  practice  the  author  has 
divided  mains  and  risers  of  steam-heating  systems  into  the  follow- 
ing classifications: 

(a)  Supply  mains  for  one-pipe  systems,  which  carry  all  water  of 
condensation,  but  in  the  direction  that  the  steam  flows. 

TABLE  I.— PIPE  SIZES  FOR  STEAM  HEATING  ACCORDING  TO  BALD- 
WIN AND  MILLS.     SQUARE  FEET  OF  HEATING  SURFACE. 

Size  of  pipe  in  inches..     1        23        45          6  8          10 

A. — Mills — Supply  mains 

and  risers    ....;......    ...      900  1,750  2,500     3,300  4,000      7,250  10,500 

B.— Baldwin  —Supply 

mains  and  risers..,..  100  400  9001,600  2,5003,600  6,40010,000 
C. — Baldwin  —  Minimum 

for  mains 1.700  3,000      5,500  8,700    16,000  22,000 

D.— Baldwin— Returns 1,650  3,700  6,200    10,000 

(b)  Mains  for  two-pipe  or  one-pipe  overhead  systems,  into  which 
there  is  no  water  of  condensation  from  the  radiators. 


74 


STEA:J  HEATING  AND  VENTILATION. 


(c)  Supply  risers  for  ordinary  one-pipe  systems  which  carry  all 
the  water  of  condensation  and  in  a  direction  opposite  to  the  flow 
of  steam. 

(d)  Risers  for  one-pipe  overhead  systems  which  carry  all  the 
water  of  condensation  but  in  the  same  direction  as  the  flow  of 
steam,  the  lowest  part  of  riser  below  last  radiator  being  solely  a 
return  pipe. 

(e)  Supply  risers  for  two-pipe  systems  which  carry  no  water 
condensation,,  except  that  due  to  the  pipes  themselves. 

In  addition  to  these  the  following  classification  is  made  for  re- 
turn pipes : 

(f)  Return  mains  for  two-pipe  and  overhead  systems  which  are 
above  the  water-line  of  the  system. 

(g)  Horizontal  return  mains  for  two  and  one-pipe  systems  which 
are  below  the  water-line. 

(h)  Return  risers  for  two-pipe  systems. 

Table  II.  herewith  gives  the  maximum  amount  of  radiation  to 
be  put  on  each  size* of  pip'e  for  the  different  classifications: 

TABLE  II.— PIPE  SIZEb  FOR  HEATING  SYSTEMS  (MONROE). 


(a) 

(b) 

(c) 

(d) 

(e) 

(f) 

(g) 

(h) 

fl 

So 

2" 

?   i 

of 

02   i 

of  -1 

F 

9 

.2 

9 

«   ^ 

I 

_d  ^ 

C3  c? 

Lri 

9 

1 

M 
Ctf    OJ 
^    ft 

IP.-' 

03      . 

3J. 

PH   a> 

.2  w 

«£• 

1| 

II 

gS, 

ft 

ft  _S 

ft 

ft 

V 

H 

4-1 

!>>  a 

>»  o  *" 

*f 

>>  o 

S  0  aJ 

do    - 

gd> 

O 

"a  § 

"a  ^  > 

!« 

gJl 

"ft  ^ 

^    o 

i*  ~*  m 

d^ 

O> 

(Q 

ftQ 

ftHO 

—  '— 

^->  <J  ^3 

•«->  PQ  S 

•S^-1 

''I. 

W 

d 

a 

02 

03° 

n 

K 

M 

S 

1 

70 

.... 

50 

60 

80 

400 

400 

250 

150 

120 

150 

200 

900 

900 

700 

2 

300 

*400 

250 

300 

400 

1,600 

1,600 

1,200 

2^2 

500 

650 

400 

500 

700 

2,600 

3,500 

2,000 

3 

750 

1,200 

700 

900 

1,200 

3,800 

8,000 

3,000 

4 

1,400 

2,000 

1,500 

1,800 

2,000 

7,000 

14,000 

.  .  .  . 

5 

2,400 

3,500 

2,500 

2,600 

3,600 

12,000 

26,000 

6 

4,000 

5,500 

3,600 

4,200 

.... 

16,000 

.... 

.... 

7 

5,500 

8,000 

30,000 

g 

7*000 

12*000 

10 

12*000 

16,000 

12 

18.000 

25^000 

The  table  here  given  represents  the  conditions  which  are  to  be 
met  with  in  ordinary  buildings,  and  exceptional  conditions  will 
have  to  be  met  with  by  the  judgment  of  the  engineer  conducting 
the  work.  It  will  be  noted  in  general  that  this  table  gives  less 


STEAM  HEATING  AND  VENTILATION.  7£ 

radiation  on  the  small  pipe  sizes  and  more  on  the  large  than  that 
by  either  Baldwin's  or  Mills'  rules.  In  small  plants,  or  in  plants, 
where  a  large  number  of  small  radiators  are  supplied  from  the 
risers,  the  number  of  radiators  on  a  given  riser  may  affect  its  size 
irrespective  of  the  amount  of  radiation.  Eisers  less  than  1  inch 
in  size  are  rarely  used  on  a  two-pipe  system,  or  less  than  1J  on  *n 
ordinary  one-pipe  system,  unless  perhaps  for  only  one  small  ra- 
diator. In  an  overhead  system  the  height  of  the  building  and  the 
consequent  number  of  radiators  on  the  riser  affect  the  size,  espe- 
cially at  the  lower  end.  In  such  a  system  it  must  be  borne  in 
mind  that  all  the  water  of  condensation  from  the  higher  radiators 
is  falling  down  the  pipe,  passing  the  connections  to  the  lower  ra- 
diators. For  such  systems  in  high  office  buildings  it  is  therefore 
well  to  make  the  risers  fairly  large  toward  the  bottom  while  the 
upper  portion  can  be  proportioned  according  to  the  sizes  given  in 
column  (d).  For  buildings  about  ten  stories  high,  the  lower  part 
of  the  riser  should  be  not  less  than  2  inches,  and  if  the  amount  of' 
radiation  on  the  riser  is  large  or  the  building  is  over  15  stories 
high,  this  may  better  be  2^  inches.  The  table  given  is  intended 
for  low-pressure  gravity  systems  and  exhaust  heating  where  not 
more  than  2  or  3  pounds  back  pressure  can  be  carried  on  the- 
engine. 

For  high-pressure  systems  working  at  20  or  30  pounds  pressure,, 
such  as  are  used  sometimes  in  factories,  when  engines  are  used 
with  a  condenser,  the  pipe  sizes  may  be  somewhat  smaller  than 
those  given  in  columns  (e)  and  (h),  although  for  the  smaller 
connections  it  is  not  advisable  to  reduce  them  on  account  of  the 
possibility  of  water  from  the  radiators  backing  into  the  supply 
pipes. 

Pipes  for  vacuum  systems. — In  vacuum  systems  in  which  the 
vacuum  is  maintained  on  the  return  side,  pipe  connections  may  be- 
reduced  very  materially,  and  Table  III,  given  herewith,  shows 
sizes  recommended  by  Messrs.  Warren  Webster  &  Company  for 
mains,  risers  and  radiator  connections  for  the  vacuum  systems 
which  they  install.  As  already  described,  their  system  is  in  prin- 
ciple an  ordinary  two-pipe  system  with  a  vacuum  pump  on  the  re- 
turns, but  also  having  the  special  feature,  of  an  automatic  thermo- 
static  valve  on  the  return  connection,  which  valve  closes  auto- 
matically when  it  is  heated  to  steam  temperature  and  opens  when 
it  becomes  cooler.  From  the  author's  experience  he  would 


76  STEAM  HEATING  AND  VENTILATION. 

sider  the  sizes  given  in  this  table  somewhat  too  small  and  would 
in  general  recommend  about  one  pipe  size  larger. 

TABLE  III.— PIPE  SIZES— WEBSTER  VACUUM  SYSTEM.. 

Sizes   of    supply 

pipes,    in %     1    iy2    2       3         4          5        6          8  10 

Maximum  sq.  ft.  on 
runs  not  over 
50  ft 100  150  400  900  2,000  4,000  8,000  12,000  30,000  60,000 

Sq.  ft.  surf,  for  long 

runs,  300  to  400  ft.     40  100  300  600  1,500  3,000  6,000  10,000  22.000  40,000 

Minimum  for  re- 
turn for  above, 
in %  %  V2  %  1  1%  lx/4  1%  2  2% 

With  vacuum  systems  which  have  a  vacuum  only  on  the  air-valve 
•connection,  such  as  the  Paul  system,  it  is  impracticable  to  reduce 
much  the  sizes  of  the  steam  pipes  below  those  given  in  Table  II, 
as  the  only  feature  of  this  system  is  that  it  keeps  pipe  and  ra- 
diators perfectly  free  from  air,  and  does  not  greatly  affect  the 
flow  of  steam  and  water  of  condensation. 

Radiator  connections. — The  connections  from  the  risers  to  the 
radiators  are  always  made  somewhat  larger  in  proportion  than  the 
mains  and  risers,  and  Table  IV  gives  sizes  which  represent  good 
practice  for  low-pressure  systems. 

TABLE   IV.— RADIATOR  CONNECTIONS. 

One-pipe  Systems.  Two-Pipe  Systems. 


r 

Max.  surf. 

' 

Max.  surf. 

in  rad. 

Supply. 

Returns. 

in  rad. 

in. 

sq.  ft. 

in. 

in. 

sq.  ft. 

% 

25 

% 

K 

40 

1 

50 

1 

% 

75 

1% 

85 

1% 

l 

120 

1% 

130 

1% 

l 

180 

Carpenter  and  Sickles'  rule  for  steam  pipe  sizes. — In  designing 
piping  for  large  systems  it  must  be  borne  in  mind  that  there  are 
many  things  which  affect  the  flow  of  steam  in  a  piping  system,  and 
special  cases  must  have  special  consideration.  Elbows,  bends  and 
valves  greatly  increase  friction  in  the  pipes.  According  to  the 
recent  investigation  of  Professor  Carpenter  and  Mr.  E.  C.  Sickles, 
as  given  in  a  paper  before  the  American  Society  of  Mechanical 
Engineers,  Volume  XX,  a  single  90-degree  elbow  is  equal  in 
frictional  resistance  to  a  length  of  pipe  equal  to  about  520 
times  the  diameter,  while  the  resistance  of  a  globe  valve  is  equal 
to  a  length  of  706  times  the  diameter,  and  a  good  gate  valve 


STEAM  HEATING  AND  VENTILATION.  77 

does  not  add  any  practical  resistance.  They  gave  the  following 
approximate  formula  for  diameters  of  pipes,  which  they  say  is 
practically  accurate  for  sizes  over  2J  inches: 

d  =  0.184  y  w*  L  H-  pD 

in  which  d  equals  the  diameter  in  inches ;  w,  the  weight  of  steam, 
to  be  delivered  in  pounds  per  minute;  L,  the  length  of  the  pipe  in 
feet;  D,  the  density  or  weight  in  pounds  per  cubic  foot,  and  p,  the 
difference  in  pressure  in  pounds  per  square  inch  between  the  ends 
of  the  pipe.  Transposed,  this  formula  becomes : 

w=  V  pDd6  -5-  0.00021  L. 

From  this  it  will  be  seen  that,  other  things  being  equal,  the  de- 
livery is  proportional  to  the  square  root  of  the  fifth  power  of  the 
diameter. 

The  accompanying  table,  Table  Y,  is  calculated  from  this  for- 
mula, assuming  p  =  1  pound  per  square  inch  difference  of  pressure 
and  D  =  0.04,  which  is  the  density  of  steam  at  a  pressure  of  about 
one  pound  above  the  atmosphere.  In  this  table  allowance  is  made 
also  for  two  globe  valves  and  two  elbows  to  each  length  of  pipe. 
The  square  feet  of  surface  each  pipe  would  supply,  allowing  0.30 
pound  of  steam  per  square  foot  per  hour  (0.005  pound  per  minute), 
which  is  very  liberal  for  direct  radiation,  is  also  given  in  the  table. 
This  table  is  chiefly  interesting  when  compared  with  Table  II> 
but  may  be  of  value  for  long  mains  where  the  building  to  be 
heated  is  at  a  distance  from  the  plant.  It  should  be  noticed,  how- 
ever, that  the  greatest  resistance  is  due  to  the  elbows  and  valves. 
For  example,  the  8-inch  pipe,  600  feet  long,  with  two  elbows  and 

TABLE  V.— CAPACITIES  OF  STEAM  PIPES. 

w  —  wt.  of  steam  delivered  per  min.  per  1  Ib.  difference  of  pressure. 
R  =  sq.  ft.  of  radiation  supplied  at  0.005  Ib.  per  sq.  ft.  per  min. 

Diameter,  Length  of  pipe  allowing  for  2  valves  and  2  elbows, 

in.  feet. 

3  w 

3  R 

4  w 
4  R 
6  w 
6  R 
8  w 
8  R 

10  w 

10  R 

12  w 

12  R 


)      200 

400 

600 

1,000 

8.1 

>       7.7 

6.9 

6.3 

5.5 

,70< 

)     1,540 

1,380 

1,22 

1,100 

15.( 

)      14.2 

12.9 

12. 

lO.b' 

00( 

)     2,840 

2,580 

2,400 

2,120 

33. 

31. 

29. 

26.2 

6,600 

6,200 

5,800 

5,240 

59.5 

56.5 

54. 

49. 

11,900 

11,300 

10,800 

9,800 

95. 

90.4 

87. 

81. 

19,000 

18.080 

17,400 

16,200 

138. 

132. 

128. 

120. 

27,600 

26,400 

25,600 

24,000 

78  STEAM  HEATING  AND  VENTILATION. 

two  valves  is  equivalent  to  2,240  feet  of  straight  pipe,  and  the 
-addition  of  another  elbow  would  be  equivalent  to  350  feet 
of  straight  pipe  and  would  reduce  the  delivery  in  the  ratio  of 
V2,240  -f-  2,590. 

Draining  pipes. — In  laying  out  the  piping  system  for  a  heating 
plant,  besides  the  proper  size  of  pipes  there  are  two  points  which 
must 'be  very  carefully  considered :  (1)  That  pipes  as  well  as  radia- 
tors are  properly  drained  so  that  the  water  of  condensation  will 
flow  off  easily  and  uniformly  to  its  proper  receptacle;  and  (2)  that 
proper  provision  be  made  for  the  expansion  of  pipes,  so  that  such 
expansion  shall  not  interfere  with  the  flow  of  steam  or  water  or 
disturb  the  setting  of  the  radiators. 

Pipes  for  an  ordinary  one-pipe  system,  which  are  run  around 
the  basement  of  a  building,  should  be  pitched  toward  the  extreme 
ends,  from  which  the  return  connection  should  be  taken  and  run 
back  to  the  receiver  below  the  water-line.  If  the  mains  are  very 
long  they  should  be  drained  at  intervals  into  this  pipe. 

In  a  two-pipe  system  in  which  the  mains  are  similarly  run,  they 
should  be  drained  into  the  return  pipes,  and  in  making  these 
drip  connections  care  should  be  taken  that  the  return  pipes  into 
which  they  drain  are  lower  than  the  supply  mains,  so  that  there 
will  be  no  opportunity  for  water  to  flow  from  the  returns  into 
the  supply  mains.  The  return  pipes  are  generally,  where  possi- 
ble, run  under  the  basement  floor,  and  should  be  lower  than  the 
supplies.  Figures  31  and  32  represent  typical  connections  from 
mains  to  risers.  Where,  on  account  of  economy  of  space,  it  is 
necessary  to  run  the  supply  and  return  mains  on  nearly  the  same 
level,  as  in  Figure  32,  the  supply  main  must  be  dripped  into  a 
separate  pipe  run  back  under  the  floor  or  along  the  wall  and  con- 
nected into  the  principal  return  main  below  the  water-line  of 
the  system.  In  two-pipe  systems  where  the  supply  mains  are 
short  and  properly  covered,  so  that  there  is  not  much  condensa- 
tion, they  may  be  given  a  slight  rise  from  the  boiler  or  source 
of  supply  and  the  water  of  condensation  allowed  to  flow  back. 
Riser  connections  should  be  taken  out  of  the  top  of  the  mains  so 
as  to  prevent  any  water  of  condensation  that  may  be  in  the  mains 
from  getting  into  the  risers. 

In  the  one-pipe  overhead  system  there  is  always  a  main  supply 
riser  running  to  the  branch  mains  in  the  attic,  and  this  should  have 
a  drain  pipe  from  its  lowest  point  extending  back  to  the  receiving 


ISTEAM  HEATING  AND  VENTILATION.  19 

tank.    The  attic  mains  are  drained  directly  into  the  supply  risers, 
which  drop  from  the  bottom  of  them. 

In  connecting  up  radiators  on  a  one-pipe  system  they  should  be 
set  so  as  to  pitch  slightly  toward  the  connection  from  the  riser, 
and  the  connection  should  always  pitch  toward  the  riser.  Con- 
nections which,  on  account  of  carelessness  in  workmanship,  were 
pitched  in  the  opposite  way,  are  a  very  fertile  cause  of  water- 
hammer.  Eadiators  set  on  two-pipe  systems  should  be  pitched 
slightly  toward  the  return  connection,  which  should  not  be  con- 
nected from  the  same  end  as  the  supply.  There  are  a  number  of 
plants  in  which  radiators  connected  on  two-pipe  systems  have 
both  the  supply  and  return  connections  at  the  same  end  of  the 
radiator,  but  in  the  opinion  of  the  author  this  is  a  very  bad  prac- 
tice, as  the  radiator  might  very  much  better  be  connected  on  the 
one-pipe  system.  In  fact,  when  radiators  with  such  connections 
are  in  operation,  unless  the  return  connection  is  lower  than  the 
supply,  which  is  not  generally  the  case,  the  water  of  condensation 
is  just  as  apt  to  Tun  down  the  supply  connection  as  down  the  re- 
turn. Furthermore,  when  such  radiators  are  turned  on,  if  the  sup- 
ply valve  is  opened  first,  any  water  which  may  be  in  the  radiator 
runs  out  of  this  connection,  as  well  as  the  large  amount  that 
is  formed  by  the  first  contact  of  steam  with  the  cold  radiator; 
and  if  the  return  valve  is  opened  first,  the  water  in  the  return 
pipe  backs  up  into  the  radiator,  so  that  when  the  supply  valve 
is  opened,  a  large  amount  of  it  will  run  out  to  the  supply  connec- 
tion. At  this  point  it  should  be  stated  that  in  turning  on  radia- 
tors with  two-pipe  connections  the  supply  valve  should  always 
be  opened  first;  and  the  fact  that  the  uninformed  occupants  of 
rooms  frequently  do  not  know  which  is  the  supply  valve  is  one 
of  the  objections  of  two-pipe  systems. 

Expansion  of  pipes. — The  expansion  of  pipes  is  an  important 
consideration  in  any  case,  and  where  there  are  long  mains  or  in 
high  office  buildings,  which  consequently  have  long  vertical  risers, 
it  becomes  a  consideration  of  vital  importance.  The  coefficient 
of  expansion  of  wrought-iron  pipe  is  0.000007  per  degree  Fahr. 
This  amounts  to  about  1.5  inches  in  a  100-foot  length  for 
low-pressure  steam  pipes.  In  horizontal  mains  this  can  be  gen- 
erally taken  care  of  by  making  turns  or  offsets  in  the  mains  in 
every  50  or  75  feet  of  pipe,  the  expansion  being  taken  up  by  the 
spring  of  the  pipe.  All  connections  from  mains  or  risers  should 


80 


STEAM  HEATING  AND  VENTILATION. 


be  made  with  sufficient  length  of  horizontal  connection  to  allow  for 
this  expansion.  In  Figures  31  and  32  the  expansion  of  the 
mains  and  risers  is  taken  up  in  the  spring  of  the  arms,  AB.  An 
old  rule  for  the  length  of  such  expansion  arms  is  that  the  length 
in  feet  should  be  equal  to  twice  the  diameter  in  inches.  This, 
is  a  fair  rule  in  most  cases,  but  much  depends  on  the  amount  of 
expansion  to  be  taken  care  of,  and  no  set  rule  can  be  given. 

The  most  serious  difficulties  on  account  of  expansion  are  met 
with  in  the  long  vertical  risers  of  the  modern  high  office  buildings. 
In  such  cases  any  considerable  movement  of  the  riser  is  apt  to  re- 
sult in  trouble,  as  the  radiator  connections  are  generally  short. 


Pipe 


Elevation.       p|O  32  Section. 


Provisions  for  Drainage  and  Expansion  of  Piping. 

Various  means  are  employed  to  overcome  this.  In  buildings  over 
ten  stories  in  height  it  can  generally  be  taken  care  of  by  anchor- 
ing the  risers  rigidly  in  the  middle  so  they  expand  in  both  direc- 
tions, and  allowing  for  the  expansion,  by  the  connections  to  the 
supply  main  in  the  attic  and  to  the  returns  in  the  basement.  The 
radiators  on  the  upper  and  lower  floors,  where  most  of  the  ex- 
pansion takes  place,  must  have  connections  sufficiently  long  to 
allow  for  it,  and  they  must  have  sufficient  pitch,  so  that  they  will 
not  be  trapped  by  the  expansion  of  the  risers.  The  author  is  fa- 
miliar with  one  building  14  stories  high  in  which  expansion  is  en- 
tirely? tak^-iir  care  of  in  this  way.  Radiators  on  the  extreme  floors 


STEAM  HEATING  AND  VENTILATION. 


81 


Radiator. 


are  made  with  extra  high  legs,  and  the  connection  from  riser  is- 
as  shown  in  Figure  33.  In  another  case,  in  a  14-story  building,, 
an  offset  was  made  in  each  riser  over  the  windows  of  the  seventh 
floor,  the  upper  part  running  on  the  opposite  side  of  the  tier  of 
windows  from  the  lower  part,  the  spring  of  the  pipe  in  this  offset- 
taking  care  of  the  expansion  at  this,  point.  The  risers  were  an- 
chored rigidly  in  the  center  of  each  section.  Arrangements  of 
this  kind  are  frequently  used,  and  the  chief  objection  is  that  un- 
less they  are  concealed  the  offsets  make  an  unsightly  appearance, 
and  it  is  frequently  very  inconvenient  to  put  them  in  on  account 
of  the  arrangement  of  the  building. 

In  one  large  16-story  building  with  which  the  author  is  ac- 
quainted, a  loop,  as  indicated  in  Fig- 
ure 34,  was  made  with  each  riser  and 
sealed  in  the  seventh  floor;  but  he 
would  not  recommend  this  arrange- 
ment, inasmuch  as  leaks  are  most  apt 
to  occur  at  the  points  marked  C  when 
the  expansion  and  contraction  works 
on  the  threads  of  the  joint.  Besides 
this,  the  framing  of  the  building  and 
extra  construction  details  in  the  floor 
necessary  to  conceal  these  offsets  are 
difficult  and  expensive.  The  expansion 
of  such  risers  is  frequently  taken  care 
of  by  means  of  expansion  joints,  a  dia- 
gram of  which  is  shown  in  Figure  35. 
The  author  has  used  these  joints  to 

a  large  extent,  and  although  in  some  localities  there  is  a  prejudice 
against  them,  he  thinks  this  rather  unwarranted.  By  proper  ar- 
rangement the  expansion  risers  in  any  building  not  over  12  or 
14  stories  high  .can  be  taken  care  of  with  one  set  of  expansion 
joints.  In  a  14-story  building  heated  on  the  overhead  system 
the  author  installed  an  expansion  joint  in  each  riser  above  the 
radiator  connection  at  the  seventh  floor.  The  risers  were  an- 
chored rigidly  to  the  beams  of  the  fifth  and  twelfth  floors  so 
that  expansion  was  in  both  directions  from  these  points.  This 
gave  about  f  inch  expansion  downward  at  the  first  and  eighth 
floors  and  about  f  inch  upward  at  the  seventh  and  fourteenth.  Ead- 
iator  connections  on  the  eighth  floor  were  long  enough  to  admit  of 


82 


STEAM  HEATING  AND  VENTILATION. 


STEAM  HBZfING  AND  VENTILATION.  83 

this  expansion,  and  on  the  first  floor  they  were  connected  as  in 
Figure  33.  If  the  radiator  connections  were  very  short,  two  joints 
would  have  been  put  on  each  of  these  risers. 

In  laying  out  large  systems,  valves  should  be  placed  on  each 
riser  so  that  each  one  can  be  shut  off  independently  of  the  others 
in  case  of  leaks  or  in  case  of  repairs  or  changes  to  be  made  on 
any  of  the  radiators.  Gate  valves  should  be  used  preferably  on 
account  of  the  fact  that  they  interpose  infinitely  less  resistance 
to  the  flow  of  steam  or  water  than  do  globe  valves.  Furthermore, 
in  such  cases  provision  should  be  made  for  changes  in  the  arrange- 
ment of  rooms  and  consequent  changes  in  the  location  of  radiators. 
It  is  a  very  good  practice  to  put  tees  on  each  riser  at  each  floor 
whether  or  not,  in  the  first  instance,  a  radiator  connection  is  re- 
quired, as  subsequent  changes  in  the  arrangement  of  rooms  may 
make  it  desirable  to  change  the  radiators. 

Figure  36  shows  the  arrangement  of  piping  in  the  attic  of  the 
Ellicott  Square,  a  large  10-story  building  in  Buffalo,  N.  Y.,  which 
is  heated  by  direct  radiation  on  the  overhead  system.  The  figure 
illustrates  the  method  of  connecting  the  overhead  mains  to  the 
risers,  and  also  the  way  in  which  expansion  of  the  mains  is  pro- 
Tided  for  by  bends  and  offsets.  In  this  instance  the  piping  was 
rigidly  anchored  at  four  points  marked  D,  and  the  expansion  al- 
lowed in  all  directions  from  these  four  points.  It  may  be  noted 
here  that  branch  mains  were  taken  off  at  points  marked  E  and  F, 
instead  of  connecting  each  riser  to  the  main  10-inch  pipe  at  these 
points.  This  was  done  for  the  purpose  of  saving  the  expense  and 
•'the  delay  to  the  work  of  connecting  each  riser  into  the  10-inch 
pipe. 

Valves. — Much  care  should  be  used  in  placing  valves  on  a  piping 
system.  Gate  valves  should  always  be  used  on  mains.  If  globe 
valves  are  used  anywhere,  the  stems  must  be  placed  horizontally, 
as  otherwise  they  form  a  water  pocket.  Thermostatic  valves,  so- 
called,  are  often  used  on  radiators,  being  connected  with  an  auto- 
matic device  which  opens  the  valve  when  the  temperature  falls, 
-and  closes  when  it  rises. 

Location  of  risers. — In  laying  out  the  floor  plans  for  the  heating 
system  of  a  large  office  building  it  is  a  mistake  to  try  to  reduce 
the  number  of  risers  to  a  minimum.  It  is  much  better  to  put  in 
risers  enough  so  that  a  radiator  can  be  placed  under  any  window 
in  the  building  without  too  long  a  connection  from  the  riser,  for 


84 


STEAM  HEATING  AND  TENTTLATION. 


in  such  buildings  one  can  never  know  what  changes  in  the  arrange- 
ment of  rooms  or  in  the  location  of  radiators  may  ultimately  be 
desired.  Figure  37  shows  the  t}rpical  floor  plan  of  the  heating 
diagrams  for  a  fourteen-story  building  in  Chicago,  showing  the 
location  of  risers  and  radiators.  This  building  is  exceptional  on 
account  of  the  large  number  of  bay  windows  and  large  amount  of 
"glass  surface.  Furthermore,  the  risers  were  all  concealed  in  the 
columns  in  the  manner  shown  in  Figures  38  and  39,  the  building 
being  framed  with  Gray  columns,  built  as  indicated.  An  expan- 


Figure   37. — Plan   Showing  Location   of  Risers   and  Radiators. 

sion  joint  was  placed  on  each  riser,  above  the  radiator  connection 
at  the  eighth  floor,  with  flange  unions  above  and  below  the  joint. 
At  these  joints  a  removable  wooden  panel  was  placed  over  each 
riser,  as  indicated  at  Figure  38,  but  otherwise  they  were  enclosed 
by  the  wire-lath  and  plaster  forming  the  ordinary  finish  of  the 
columns.  Figure  39  shows  a  section  of  the  column  at  the  four- 
teenth floor.  The  radiator  connections  were  exposed  above  the 
floor  and  run  about  as  indicated  on  the  floor  plan.  This  building 
is  heated  on  the  one-pipe  overhead  system.  It  contains  11,000 
square  feet  of  radiation,  supplied  by  an  8-inch  main  to  the  attic. 
The  typical  floor  has  1,055  square  feet  of  glass  surface, 


STEAM  HEATING  AND  VENTILATION. 


85 


square  feet  of  wall  surface  and  47,400  cubic  feet  of  space,  includ- 
ing corridors,  and  is  heated  by  18  radiators  containing  787  square 
feet  of  surface.  By  the  author's  formula  given  on  page  68  the 
amount  of  surface  required  amounts  to  730  square  feet>  but  the 
exposure  of  the  upper  stories  of  this  building  is  unusually  severe. 
It  is  frequently  a  very  difficult  matter  to  conceal  risers  in  fire- 
proof buildings  on  account  of  the  floor  plates  of  the  columns  and 
the  beams,  which  frequently  interfere  with  placing  the  risers  very 
close  to  them.  Figure  40,  however,  represents  the  manner  in 
which  they  were  enclosed  in  a  building  which  was  framed  with 
~box  columns..  In  this  case  the  tile  fireproofing  was  put  on  over 
both  column  and  riser.  In  concealing  risers  in  the  walls  of  wooden 
buildings  it  is  necessary  to  protect  the  pipes  carefully  from  imme- 
diate contact  with  the  woodwork.  In  hanging  risers  in  buildings 


Fio.38 


FiG.39  FiG.4O 

Methods  of  Running  Risers  in  Columns. 


great  care  must  be  taken  that  the  pipe  be  cut  to  the  proper  lengths 
so  that  the  fittings  for  the  radiator  connections  will  come  exactly 
in  the  proper  place. 

Riser  anchors. — As  previously  stated,  risers  are  usually,  espe- 
cially in  large  buildings,  anchored  rigidly  at  certain  points  so  that 
expansion  shall  be  in  both  directions  from  these  points.  This 
should  be  carefully  done  so  that  the  pipe  will  not  slip,  and  the 
method  to  be  employed  to  accomplish  this  depends  largely  upon 
the  local  conditions.  Figures  41  and  42  show  two  methods  of  ac- 
complishing this,  the  latter  being  especially  adaptable  where  the 
riser  can  be  run  close  to  the  floor  beam,  but  to  make  it  perfectly 
rigid  it  should  be  made  strong  and  shrunk  in  place.  The  method 
indicated  by  Figure  41  can  be  adapted  to  anchoring  the  pipe  to 
a  column  instead  of  to  the  floor  beams.  In  some  cases  risers  are 
also  secured  at  the  other  floors  so  as  to  allow  expansion,  but  at 


86 


STEAM  HEATING  AND  VENTILATION. 


the  same  time  maintain  proper  alignment ;  but  this  is  not  generally 
necessary,  as  the  rigidity  of  the  piping  and  connections  is  gener- 
ally sufficient  to  keap  the  pipes  property  in  line. 

Protecting  pipes. — Where  risers  or  other  pipes  run  through  the 
floors  or  walls  they  are  generally  protected  by  floor  sleeves  with 
floor  and  ceiling  plates.  These  are  usually  made  of  galvanized 
iron  in  a  telescopic  form  so  as  to  fit  any  thickness  of  floor.  In 
buildings  with  wooden  floors  they  are  necessary  so  as  to  give  an 
air  space  around  the  pipe  and  prevent  immediate  contact  of  the 
steam  pipe  with  the  woodwork.  In  fireproof  buildings  they  ara 


FiG.4t 


Types  of  Riser  Anchors. 


frequently  omitted,  but  it  is  preferable  to  use  them,  as  they  make 
a  better  finish  around  the  pipe  at  the  ceiling  and  prevent  the  ex- 
pansion of  the  pipe  from  disturbing  the  flooring  or  plaster.  Floor 
and  ceiling  plates  should  be  used  in  any  case. 

Eadiator  connections  are  frequently  encased  in  the  floor,  but 
it  is  generally  difficult  to  accomplish  this  in  fireproof  buildings, 
as  the  space  between  the  floor  level  and  the  top  of  the  iron  beams 
is  not  generally  sufficient  to  box  in  the  connections  and  make 
proper  allowance  for  the  vertical  movement  of  these  connections 
due  to  riser  expansion.  It  can  be  done  in  some  cases,  however, 
but  the  connections  should  always  be  enclosed  in  a  galvanized-iron 
box  and  the  flooring  should  be  so  laid  that  a  strip  over  the  pipes 
can  be  easily  removed. 

Supporting  pipes. — Horizontal  pipes  are  almost  invariably  sup- 


STEAM  HEATING  AND  VENTILATION. 


87 


ported  from  the  ceiling  above  by  means  of  some  kind  of  an  expan- 
sion hanger,  two  common  types  of  which  are  shown  in  Figures 
43  and  44,  the  two  shown  in  each  case  being,  one  for  wooden  beams 
and  the  other  for  iron.  The  rods  can  be  cut  to  the  length  desired 
after  the  pipe  is  in  place.  There  is  sufficient  movement  of  the  rod 
at  the  top  to  allow  for  the  small  play  of  the  pipe  due  to  expan- 
sion. A  simple  and  cheap  form  of  hanger  frequently  used  for 
small  pipes  in  buildings  with  wooden  floors  is  made  of  a  piece  of 
light  chain  looped  under  the  pipe  and  hung  from  the  nails  in  the 
floor  beams.  The  chain  can  be  cut  to  length  with  wire  nippers. 
In  case  of  very  large  pipes  in  the  basement  of  buildings,  they  are 


FiG.43a.  Fio.43b 

Ti 

Expansion  Pipe  Hangers. 


sometimes  supported  by  some  kind  of  a  standard  erected  from 
the  floor. 

Arrangement  of  pipes. — In  laying  out  the  main  piping  connec- 
tions of  the  power  plant  of  a  large  building  great  care  must  be 
taken  to  arrange  the  pipes  as  systematically  as  possible  so  that 
they  take  up  no  more  room  than  necessary,  and  also  to  properly 
provide  for  the  drainage  of  all  pipes  into  proper  receptacles.    This- 
is  frequently  a  difficult  matter,  but  one  can  hardly  give  too  much 
consideration  to  the  subject,  as  the  successful  operation  of  a  plant 
depends  largely  upon  the  way  piping  connections  are  arranged. 
It  is  impossible  to  give  any  detailed  rules,  as  each  plant  is  a  prob- 


88 


STEAM  HEATING  AND  VENTILATION. 


STEAM  HEATING  AND  VENTILATION. 


89 


lem  in  itself,  and  is  entirely  subject  to  local  conditions.  The  main, 
connections  to  the  heating  system  must  be  laid  out  in  connection 
with  the  exhaust  and  live-steam  pipes  of  the  power  plant,  accord- 
ing to  the  principles  established  in  Chapter  II.  Simplicity  in  n 
piping  system  is  always  primarily  desirable,  but  sufficient  valves 
and  by-passes  should  be  installed,  so  that  if  any  accident  occurs 
to  one  part  of  the  system  that  part  can  be  shut  off  without  crip- 
pling more  than  a  small  section. 

Figure  45  shows  the  arrangement  of  the  main  piping  connec- 
tions in  a  large  office  building  in  Syracuse,  N.  Y.,  in  which,  on 
account  of  the  extreme  difference  in  floor  levels  and  the  crowded 
condition  of  the  machinery,  a  really  systematic  arrangement  of 
piping  it  was  impossible  to  obtain.  (The  Engineering  Record  of 
November  5,  1898.)  The  main  valves  controlling  the  heating  sys- 


Fis.44a. 


tern  are  indicated  at  A,  B,  C  and  D.  During  the  heating  season 
the  valve,  D,  is  opened  and  the  back-pressure  and  reducing-press- 
ure  valves  put  into  service,  while  during  the  summer  months  the 
valve,  D,  is  closed  entirely,  shutting  off  the  heating  mains,  and 
the  10-inch  back-pressure  valve  is  opened  wide.  Ordinarily,  both 
in  winter  and  summer,  the  valve,  A,  is  closed,  so  that  all  exhaust 
steam  from  the  pumps  and  engines  goes  through  the  muffler  tank 
and  heater;  but  in  case  it  is  necessary  to' open  these  for  cleaning, 
the  valves  B  and  C  are  closed  and  the  valve,  A,  opened,  so  that 
the  exhaust  steam  may  go  directly  either  into  the  free  exhaust 
or  the  heating  system,  as  the  case  may  be.  The  building  in  ques- 
tion contains  about  15,000  square  feet  of  radiators  and  is  heated 
on  a  two-pipe  system  with  basement  mains.  The  returns  come 
back  to  the  two  automatic  governors  which  control  the  6x4x6-' 


90  STEAM  HEATING  AND  VENTILATION. 

inch  pumps.  These  deliver  the  return  water  through  the  closed 
heater  into  the  boilers.  There  are  three  pumps  used  for  this  pur- 
pose, and  so  connected  that  any  one  can  be  used  on  the  governors 
separately  or  together,  and  any  one  can  be  used  to  pump  cold 
water  through  the  heater.  The  feed  pipe  has  a  by-pass  around 
the  heater,  to  be  used  when  the  heater  is  being  cleaned. 

Eeturn  pipes  should  be  given  as  much  pitch  as  possible  except 
where  they  are  below  the  water-line  of  the  system.  In  running 
these  below  basement  floors  they  should  be  put  in  trenches,  prefer- 
ably of  brick  or  concrete,  and  with  movable  covers.  If  there  is 
danger  of  water  underground  the  trenches  must  be  arranged  so 
that  they  can  be  kept  dry,  and  no  better  trench  can  be  made  than 
one  of  good  concrete. 

Pipe  coverings. — All  the  piping  connections  should,  as  far  as. 
possible,  be  covered  with  some  kind  of  non-conducting  pipe  cov- 
ering, of  which  there  are  innumerable  varieties  made.  In  some 
cases  risers  and  other  pipes  are  left  uncovered  so  as  to  utilize  the- 
heating  effect,  but  the  disadvantage  of  this  is  that  heat  is  given 
out  from  such  pipes  whether  it  is  wanted  or  not,  and  it  is  much 
better  practice  to  cover  the  risers  and  depend  on  the  radiators, 
for  heating.  One  of  the  greatest  sources  of  fuel  waste  is  found 
in  uncovered  mains  in  basements  of  buildings  where  heat  is  noth- 
ing but  an  inconvenience,  and  in  order  to  dispel  it  in  moderate 
weather  windows  are  opened,  which  greatly  increase  the  wasteful 
condensation.  A  good  pipe  covering  will  save  from  65  to  80  per 
cent,  of  the  heat  which  would  ordinarily  be  wasted  from  the  pipes. 
Coverings  of  which  85  per  cent,  is  carbonate  of  magnesia,  certain 
molded  forms  of  pure  asbestos  fiber,  and  molded  forms  of  mineral 
wool  are  the  best  kinds  of  protection  for  steam  pipes  to  reduce 
condensation.  Some  coverings  which  show  very  good  results  when 
new,  deteriorate  rapidly,  due  to  the  charring  effect  of  the  pipes  and 
to  disintegration. 

Pipes  and  flues  for  indirect  radiators. — "We  come  now  to  the  con- 
sideration of  certain  details  of  construction  which  are  especially 
requisite  in  indirect  heating.  In  this  class  of  steam  heating  the 
piping  connections  are  subject  to  much  the  same  rules  for  run- 
ning pipes  as  those  for  direct  radiators,  but  indirects  are  almost 
invariably  located  in  the  basement  of  buildings  and  the  pipes  run- 
ning to  them  are  horizontal.  Furthermore,  the  condensation  per 
square  foot  of  indirect  radiator  is  from  25  to  50  per  cent,  more 


STEAM  HEATING  AND  VENTILATION. 


91 


than  that  per  square  foot  of  direct  radiatpr,  so  that  the  piping 
connections  are  generally  made  about  a  size  larger,  and,  except 
in  rare  cases,  connected  on  two-pipe  systems.  Indirect  radiators 
are  usually  hung  from  the  beams  of  the  first  floor,  and  various 
methods,  which  are  dependent  upon  the  local  conditions,  are 
adopted  for  supporting  them.  A  frequent  form  of  support  is  in- 
dicated in  Figure  46,  the  radiator  resting  on  short  pieces  of  pipe 
which  are  hung  by  rods  bolted  to  the  floor  joists,  or  hung  from  a 
pipe  over  them.  Indirect  radiators  are  always  encased  in  some 
kind  of  a  metal  box,  either  of  galvanized  iron  or  tin,  or  of  wood 
lined  with  tin.  These  boxes  connect  directly  with  the  hot-air 
flues  which  run  to  the  rooms  above  and  which  are  of  heavy  tin 
or  sheet  iron.  Both  the  flues  and  boxes  should,  of  course,  be  as 
nearly  air  tight  as  possible.  In  regard  to  sizes  of  hot-air  flues,  an 


loor  L  ire  i    /  Pipz  doorf  1 

WrJoists- 

1  1 

c 

Fadiator. 

\ 

/'Floor  Line. 


% 

j)  :  ( 
Joists. 

n 

Radiator. 

Pipe  about  2."  / 

Figure  46. — Indirect  Radiator  Support. 


10 

1.2 


15 
1.0 


20 

0.85 


25 
0.75 


old  rule  gives  1  square  inch  of  flue  area  to  1  square  foot  of  radia- 
tor. This  is  very  satisfactory  in  most  cases,  but  the  following 
table,  which  gives  the  sizes  recommended  by  Prof.  J.  H.  Kinealy, 
is  to  be  preferred,  as  the  size  of  flue  should  depend  upon  its  height : 

SIZES  OF  FLUES   FOR  INDIRECT   RADIATORS. 

Height  in  feet  from  center  of  radiator  to 

center  of  register 5 

Sq.  in.  of  flue  area  for  1  sq.  ft.  radiation 1.7 

The  indirect-radiator  boxes  must,  of  course,  have  a  fresh-air 
inlet.  This  should  always  be  run  from  the  outside  and  from  a  lo- 
cation removed  from  the  possibility  of  contamination  to  the  in- 
coming air;  and  it  is  preferable  that  the  cold-air  inlet  be  located 
at  least  a  few  feet  above  the  ground.  Cold-air  supply  connections 
from  the  outside  to  indirect  boxes  should  be  made  as  short  as  pos- 
sible; 1  square  inch  area  per  1  square  foot  is  generally  sufficient, 


STEAM  HEATING  AND  VENTILATION. 


although  if  the  flues  a:ce  of  considerable  length  or  are  winding,  a 
larger  ratio  should  be  given.  If  a  number  of  radiators  receive 
air  from  the  same  cold-air  flue,  the  flue  may  be  somewhat  smaller. 
In  buildings  in  which  there  are  a  considerable  number  of  indirect 

radiators  there  are  two 
general  methods  of  con- 
necting the  fresh-air 
flues,  which  are  illus- 
trated in  Figures  47  and 
48.  Figure  47  represents 
the  cellar  plan  of  a  large 
Massachusetts  residence 
(The  Engineering  Bec- 
ord,  August  5,  1893;  Mr. 
A.  A.  Sanborn,  Boston, 
heating  contractor),  in 
which  there  are  seven 
large  clusters  of  indirect 
radiators  which  supply 
about  30  hot-air  flues  ris- 
ing to  the  rooms  above, 
the  hot-air  pipes  run- 
ning horizontally  from 
the  radiator  boxes,  in 
some  cases  for  50  feet, 
to  the  vertical  flues. 
radiators  in  this 
are  all  Gold's 
Pin  in  16-foot  sections.) 
In  the  Philadelphia  resi- 
dence shown  in  Figure 
48  (The  Engineering 
Eecord,  December  15, 
1894),  there  is,  on  the 
contrary,  a  long  main 
cold-air  duct  which  sup- 
plies a  large  number  of 

indirect  radiators,  one  for  each  of  the  vertical  flues,  the  radiator 
in  all  cases  being  located  directly  under  the  vertical  flues.  In 
the  opinion  of  the  author  this  is  much  the  preferable  method, 


(The 


building 


STEAM  HEATING*  AND  VENTILATION. 


93 


as  a  much  more  positive  circulation  of  air  to  the  separate  rooms 
can  be  secured  than  by  the  other  method. 

The  system  shown  in  Figure  48  is  interesting  also  on  account  cf 
the  construction  of  the  main  cold-air  duct  and  the  connections 
from  it  to  the  radiator  boxes.  These  are  well  illustrated  in  Figure 
49,  the  main  duct,  it  will  be  noted,  being  of  brick,  and  underground. 
In  the  author's  opinion  there  is  one  particular  in  which  the  system 
shown  in  Figure  48  might  have  been  much  improved.  The  colcl- 
air  duct  is  long  and  winding,  and  had  it  been  more  uniform  in  size 


Figure  48. — The  Indirect  System  in  a  Philadelphia  Residence. 

and  supplied  with  another  cold-air  connection  on  the  side  of 
house  opposite  the  existing  one,  it  would  have  insured  a  more  posi- 
tive circulation  to  all  the  radiators.  The  reason  of  this  is  that 
in  cases,  such  as  shown  in  Figure  48,  where  there  is  only  one  cold- 
air  connection  for  a  number  of  radiators,  when  there  is  a  strong 
wind  blowing  against  the  side  of  the  house  opposite  the  fresh-air 
inlet  it  is  sometimes  very  difficult  to  get  a  good  draft  in  the  flues, 
especially  in  those  most  removed  from  the  cold-air  inlet,  as  the 
force  of  the  wind  (which,  with  the  best  constructed  houses,  blows 
through  the  walls  to  a  great  extent),  seriously  opposes  the  current 


94  STEAM  HEATING  AND  VENTILATION. 

of  air  in  the  ducts.  If  there  are  two  fresh-air  connections,  each 
provided  with  dampers,  the  one  on  the  leeward  side  of  the  build- 
ing can  be  closed  and  the  one  on  the  windward  side  opened  to  give 
a  proper  amount  of  cold  air.  It  is,  moreover,  desirable  to  put  a 
tight  damper  in  the  duct  to  each  radiator. 

Setting  direct-indirect  radiators. — In  regard  to  the  setting  of  di- 
rect-indirect radiators,  the  piping  connections  are  made  according 
to  precisely  the  same  rule  as  for  directs,  although  in  cases  of  large 
radiators  of  this  kind  it  may  be  desirable  to  increase  slightly  the 
pipe  sizes  on  account  of  the  somewhat  increased  condensation.  A 


Plan 

first floor  Register, 


Indirect 
Radiator: 


Elevation. 

Cellar  Floor. 


Brick 
Duct. 


F.G.49 

THE  ENGINEERING  RECORD. 

frequent  form  of  fresh-air  connection  for  this  kind  of  radiator  is 
indicated  in  Figure  50,  and  the  connection  to  the  outside  air  should 
in  all  cases  be  provided  with  an  easily  adjusted  damper.  One 
trouble  with  direct-indirect  radiators  is  that  when  a  strong  wind 
is  blowing  against  the  outside  wall  it  is  difficult  to  prevent  objec- 
tionable drafts,  due  to  sudden  gusts  of  wind,  which,  in  cold  weath- 
er, will  make  frequent  cold  waves  across  a  room  notwithstanding 
the  average  temperature  may  be  about  right.  Figure  51  represents 
a  special  form  of  setting  for  large  radiators  of  this  kind  adopted 
%  Mr.  Alfred  E.  Wolff,  in  the  Singer  Building,  New  York  City. 
(The  Engineering  Record,  September  3,  1898.)  It  will  be  seen 
that  the  effect  mentioned  is  here  avoided  by  making  the  cold-air 


STEAM  HEATING  AND  VENTILATION. 


95 


Iiilet  to  the  radiator  somewhat  tortuous,  so  that,  as  far  as  possible, 
the  draft  is  due  only  to  the  hot  air  from  the  radiator.  The  same 
effect  is  accomplished  in  the  United  States  Government  method 


Inlet  Damper. 

~~  — -___ 

"TMS  ENOINECRINO  RECORD. 

Figure  50.— A  Direct-Indirect  Radiator. 


Fie. 51 
Types  of  Direct-Indirect  Radiator  Casings. 

of  setting  indirects  in  the  Detroit  Post  Office,  which  is  shown  in 
Figure  52.  Mr.  Henry  Adams,  of  Baltimore,  Md.,  was  the  engineer 
for  this  work.  (The  Engineering  Eecord,  August  7,  1897.) 


CHAPTER  VII.— MECHANICAL  VENTILATION- 
GENERAL  PRINCIPLES. 

Need  of  proper  ventilation. — It  may  be  stated  as  an  undeniable 
truth  that  no  system  of  ventilation  is  adequate  to  give  proper 
results  at  all  times  and  in  all  kinds  of  weather,  unless  it  is  a  me- 
chanical system.  As  has  been  seen  in  a  previous  chapter,  the  air 
discharge  of  an  ordinary  ventilating  flue  with  the  gravity  system 
depends  upon  the  difference  in  temperature  between  the  air  in  the 
flue  and  the  outside  air,  so  that  its  discharge  is  very  different  in 
moderate  from  what  it  is  in  very  cold  weather.  Very  satisfactory 
results  are  in  many  cases  obtained  from  indirect  radiators,  but  the 
same  is  true  of  these  as  of  an  ordinary  ventilating  flue.  And  every 
one  now  knows  of  the  precarious  nature  of  ventilation  by  open 
doors  and  windows,  since  in  cold  weather  the  occupants  of  rooms 
invariably  prefer  warm  and  bad  air  to  that  which  is  cold  and  fresh. 
Yet  those  who  have  been  interested  in  the  subject,  for  as  long  as 
a  decade,  can  readily  recall  the  days  when  such  means  of  ventila- 
tion were  considered  entirely  sufficient  even  for  schools,  churches 
and  other  densely-peopled  buildings.  It  is  part  of  the  marvelous 
scientific  development  of  the  close  of  the  nineteenth  century  that 
there  has  been  such  an  advance  in  the  popular  appreciation  of  the 
necessity  and  value  of  good  ventilation,  that  a  very  fair  percent- 
age of  school-houses  now  erected,  even  in  the  smaller  communities, 
boasts  of  a  complete  ventilating  plant. 

There  are,  however,  many  such  plants  that  are  in  reality  not 
the  perfect  ones  they  are  made  to  appear,  and  the  problems  con- 
nected with  the  proper  distribution  of  an  adequate  volume  of  air 
to  and  through  buildings  and  rooms  of  various  kinds  are  more 
varied  and  complicated  than  is  ordinarily  supposed.  Only  those 
who  have  had  much  experience  with  them  and  who  have  met  with 
failures  in  some  of  their  cherished  schemes  of  ventilation,  realize 
that  air  is  a  very  subtle  medium  of  control.  It  is  a  comparatively 
simple  matter  to  obtain  a  large  blower  and  connect  it  by  a  system 
of  ducts  to  the  rooms  to  be  ventilated,  but  to  admit  the  air  into 
the  rooms  in  sufficient  volume  without  drafts  and  make  it  circu- 
late where  it  is  needed  is  a  different  proposition.  The  air  currents 


STEAM  HEATING  AND  VENTILATION.  97 

have  an  exasperating  way  of  going  around  the  ceiling  instead  of 
across  the  breathing  line;  or  of  running  down  walls  and  out  of 
doorways  instead  of  across  the  room  and  out  of  properly-prepared 
vent  openings.  Another  source  of  tribulation  is  the  fact  that  in 
winter  the  temperature  of  the  fresh  air  blown  in  is  in  most  cases 
warmer  than  the  average  temperature  of  the  room;  while  in  sum- 
mer it  is  somewhat  cooler,  so  that  in  the  former  case  the  incom- 
ing air  tends  to  go  to  the  ceiling.,  and  in  the  latter  to  the  floor. 

There  are  a  few  old-time  fallacies,,  vestiges  of  which  still  linger 
to  a  surprising  degree  in  the  minds  of  many  who  appreciate  the 
necessity  of  good  ventilation.  Among  these  are  the  ideas  that 
fresh  air  must  be  cold  and  that  it  must  be  admitted  through  win- 
dows, and  the  foul  air  be  drawn  off  through  vent  flues-.  But  the 
worst  of  all  is  one  of  the  carbonic-acid  theories,  which  is  to  the 
effect  that  exhaled  air  is  laden  with  carbonic-acid  gas  (C02),  which, 
being  heavier  than  pure  air,  sinks  to  the  floor,  and  may  be  tapped 
off  by  putting  an  outlet  anywhere  at  the  floor-level.  This  notion 
seems  to  be  firmly  grounded  into  the  minds  of  many,  who  cling 
to  it  steadfastly.  It  is  difficult  to  explain  to  these  unfortunates 
that  the  air  exhaled  by  man  contains  ordinarily 'less  than  5  per 
cent,  of  carbonic  acid,  which  would  not  affect  the  specific  gravity 
to  an  appreciable  degree;  and  that  furthermore  there  is  an  indis- 
putable natural  law  known  as  the  diffusion  of  gases,  in  accordance- 
with  which  two  gases  in 'contact  tend  to  form  a  perfect  mechan- 
ical mixture. 

The  carbonic-acid  gas  in  the  air  of  rooms  is,  however,  an  impor- 
tant consideration,  as  it  serves  as  an  accurate  index  of  the  degree 
of  vitiation.    It  must  be  understood,  of  course,  that  the  carbonic- 
acid  gas  in  itself  is  not  injurious  and  is  merely  an  index.    The  air 
of  the  stuffiest  lecture  room  that  one  ever  goes  into  does  not  con- 
tain more  than  50  parts  in  10,000,  and  air  that  contains  as  much 
as  15  parts  in  10,000,  due  to  being  repeatedly  breathed,  is  of  a, 
very  unhealthy  quality.    Notwithstanding  this,  in  soda-water  fac- 
tories the  air  frequently  contains  as  much  as  150  or  200  parts  of; 
C02  to  10,000,  and  is  in  no  way  injurious.   In  air  that  contains  as, 
much  as  10  or  15  parts  of  C02  in  10,000,  due  entirely  to  exhala-. 
tions  from  the  body,  it  is  not  so  much  the  C02  that  constitutes  the 
obnoxious  element,  as  it  is  the  organic  matter  and  the  germ-laden 
moisture  that  accompanies  it — not  necessarily  disease  germs,  but 
all  kinds  of  natural  germs,  which  are  more  or  less  injurious,  and 


»8  STEAM  HEATING  AND  VENTILATION. 

which,  together  with  the  organic  matter  given  off  in  the  moisture 
of  the  breath,  gives  to  confined  air  that  oppressive  and  stuffy  ef- 
fest  which  is  at  once  disagreeable  and  exceedingly  unhealthful. 

It  is  not  intended  here  to  go  into  detail  in  regard  to  the  ill  effects 
of  breathing  vitiated  air  and  the  hygienic  value  of  good  ventilation. 
The  absurdity  of  expecting  to  develop  bright  and  healthy  children 
by  sending  them  day  after  day  to  shut-up  school  rooms,  or  of  ex- 
pecting inspiring  results  from  sermons  or  lectures  delivered  in 
close  and  stuffy  halls,  or  of  having  popular  reading  rooms  or  thea- 
ters where  the  air  is  laden  with  the  peculiar  aroma  of  a  mixed  and 
varied  populace,  is  rapidly  being  better  and  better  understood,  and 
more  and  more  widely  appreciated. 

There  is  no  doubt  but  that  in  a  large  room  which  is  occupied  for 
some  length  of  time  by  a  crowded  assembly  it  is  impossible  to  se- 
cure air  of  the  same  purity  as  that  outside,  as  the  breath  from 
the  occupants  vitiates  the  incoming  air  as  well  as  that  which  is 
already  in  the  rooms.  In  other  words,  it  is  impossible  for  the 
occupants  of  a  room  to  inhale  pure  incoming  air  and  exhale  it  so 
that  it  will  pass  out  by  a  vent  shaft  without  a  portion  of  it  com- 
ing in  contact  with  anyone  else.  If  this  were  the  case  it  would 
only  be  necessary  to  supply  from  12  to  15  cubic  feet  of  air  per 
person  per  hour,  which  is  about  the  rate  of  breathing  of  adults,  in 
order  to  insure  perfect  ventilation.  As  a  matter  of  fact,  however, 
the  best  we  can  do  is  to  dilute  the  vitiated  air  as  much  as  possi- 
ble, and  it  has  been  found  that  to  accomplish  this  to  a  satisfactory 
degree  requires  from  100  to  200  times  the  amount  of  air  above 
mentioned  per  person  per  hour. 

Pure  air  is  found  by  investigation  to  contain  very  close  to  4  parts 
of  C02  in  10,000.  The  opinions  of  many  able  hygienists  agree  that 
when  the  proportion  of  C02  exceeds  6  parts  in  10,000  the  bad 
effects  of  poor  ventilation  begin  to  be  noticeable,  and  when  8 
parts  in  10,000  are  found,  the  characteristic  odor  of  an  ill-venti- 
lated room  is  apparent;  and  to  those  who  remain  in  such  an  at- 
mosphere for  any  length  of  time  there  comes  a  feeling  of  close- 
ness, lassitude  and  dullness.  It  is  therefore  universally  agreed 
that  when  the  carbonic  acid  is  formed  entirely  by  the  breathing 
of  the  occupants,  the  quantity  should  not  exceed  6  parts  in  10,000, 
though  8  parts  may  in  some  cases  be  permitted  for  short  periods, 
and  that  anything  in  excess  of  this  figure  indicates  poor  ventila- 
tion. 


STEAM  HEATING  AND  VENTILATION.  99 

Air  required  for  ventilation. — The  amount  of  fresh  air  required 
depends  upon  the  number  of  people  and  the  amount  of  carbonic- 
acid  gas  given  off  by  each  individual  in  breathing.  This  last  factor 
is  exceedingly  variable,  depending  upon  the  weight,  age  and  physi- 
cal, as  well  as  mental,  condition  of  the  person.  Pettenkofer,  a 
very  painstaking  scientist,  gives  the  following  figures  for  the  aver- 
age amount  of  carbonic-acid  gas  given  off  per  hour  by  adults  per 
pound  of  weight: 

In  repose 0.00424  cubic  feet. 

In  general  exercise 0.00591  cubic  feet. 

In  hard  work 0.0122    cubic  feet. 

In  sleep,  about 0.00320  cubic  feet. 

He  also  adds  that  the  amount  given  off  by  young  children  is  nearly 
twice  as  much  per  pound  of  weight  as  for  adults.  Some  diseases, 
such  as  fever,  increase  the  amount,  and  others  decrease  it.  Pet- 
tenkofer's  figures  would  make  the  average  for  persons  in  repose 
about  as  follows: 

Males  (160  pounds  weight) 0.68  cu.  ft.  per  hr. 

Females  (120  pounds  weight) 0.51  cu.  ft.  per  hr. 

Children  (80  pounds  weight) 0.68  cu.  ft.  per  hr. 

Parkes,  in  his  work  on  hygiene,  gives  as  the  amount  of  carbonic- 
acid  gas  given  off  during  repose  the  following: 

Males  (160  pounds  weight) 0.72  cu.  ft.  per  hr. 

Females  (120  pounds  weight) 0.60  cu.  ft.  per  hr. 

Children  (80  pounds  weight) 0.40  cu.  ft.  per  hr. 

Average  mixed  community 0.6    cu.  ft.  per  hr. 

These  figures  show  some  variation  from  Pettenkof er's ;  but  cer- 
tainly for  adults  the  variation  is  not  more  than  might  be  found  in 
two  sets  of  individuals.  It  is  very  generally  accepted  by  hygienists 
that  0.6  cubic  foot  per  hour  represents  a  very  fair  average  for 
such  mixed  assemblies  as  are  found  in  theaters,  lecture  rooms, 
churches,  etc. 

The  amount  of  air  required  per  person  per  hour  to  maintain 
the  air  of  a  room  at  a  certain  standard  of  purity  may  be  worked 
out  by  a  simple  algebraic  calculation,  as  follows : 

Let  V  be  the  volume  of  air  required  per  person  per  hour  for 
continuous  occupation: 

N,  the  number  of  persons  in  the  room; 

E,  the  number  of  parts  of  C02  gas  to  be  allowed  per  10,000,  the 
number  of  parts  in  the  fresh  incoming  air  being  4; 


100  STEAM  HEATING  AND  VENTILATION. 

C,  the  total  number  of  cubic  feet  of  C02  acquired  by  the  air  of 
the  room  per  hour; 

10,000  C 
Then  R  =  -  , 

VN 

VIST  X  4 

But  C  =  --  h  0.6  N, 
10,000 

VN  X  4  +  6,000  N" 
So  that  E  =  -      -  . 


VN 

Solving  this  equation  with  N  =  1,  we  find  V  =  6,000  -f-  (R  —  4). 
For  R  =  6,  we  have  V  =  3,000;  f  or  R  =  7,  V  =  2,000;  while  if  we 
allow  R  =  8,  we  have  V  =  1,500. 

Now  if  the  room  is  of  large  volume  and  is  only  to  be  occupied 
for  a  short  period,  and  before  occupancy  the  air  is  brought  to  the- 
same  standard  of  purity  as  the  outside  air,  then  a  less  amount  of 
air  is  required.  For  example,  if  the  room  contains  500  cubic  feet 
of  space  per  person  and  is  to  be  occupied  but  one  hour,  then  ob- 
viously 3,000  —  500  =  2,500  cubic  feet  will  have  -to  be  supplied 
the  first  hour  to  have  the  air  within  the  standard  of  6  parts  of 
carbonic  acid  gas  per  10,000. 

We  may  reduce  this  to  algebraic  form  as  follows: 

Let  V  be  as  already  given  ; 

v,  the  volume  per  person  per  hour  for  a  short  occupancy, 
H,  the  number  of  hours  to  be  occupied, 

and  Y,  the  cubic  feet  of  space  in  the  room  per  person. 

Y 

Then  v  =  V  --  . 
H 

From  this  formula  Table  No.  1  is  calculated. 

TABLE  NO.  1.—  THE  VOLUME  OF  AIR  TO  BE  SUPPLIED  PER  PERSON 
PER  HOUR  THAT  THE  PURITY  OF  THE  AIR  AT  THE  END  OF   THE 
OCCUPANCY  WILL  NOT  EXCEED  THE  AMOUNT  GIVEN. 
Number  of  hours  to  be  occupied. 


space  in      Parts  of  CO2  in  10,000  not  to  be  exceeded  at  end  of  occupancy, 
room  per       67            8                678                 67 

person. 

Cubic  feet  to  be  supplied  per  person  per  hour. 

100 

2,900     1,900     1.400 

2,950     1,950     1,450 

2,970     1,970     1,470 

200 

2,800     1,800     1,300 

2,900     1,900     1,400 

2,935     1,935     1,435 

300 

2,700     1,700     1,200 

2,850     1,850     1,350 

2,900     1.900     1,400 

400 

2,600     1,600     1,100 

2,800     1,800     1,300 

2,870     1,870     1,370 

600 

2,400     1,400        900 

2,700     1,750     1,250 

2,800     1,800     1,300 

900 

2,100     1,100        800 

2,550     1,550     1,050 

2,700     1,700     1,200 

STEAM  HEATING  AND  VENTILATION.  101 

Prom  the  figures  given  it  will  be  seen  that  the  quantity  of  air  to 
be  supplied  per  person  depends  upon  the  size  of  the  room  and  the 
length  of  time  it  is  occupied  as  well  as  the  standard  of  purity  de- 
manded. 

The  standard  of  purity  to  be  required  depends  somewhat  upon, 
the  nature  of  the  room.  Some  rooms,  such  as  churches,  lecture 
rooms,  theaters,  libraries,  and  some  reading  rooms,  are  occupied 
by  widely  varying  numbers  of  people,  being  sometimes  very 
crowded  and  sometimes  but  partially  filled;  while  others,  school 
rooms  and  hospitals  in  particular,  are  occupied  almost  always  by 
about  the  same  number.  Of  the  former  class,  if  the  cubic  feet  of 
air  required  is  based  upon  the  maximum  crowded  capacity,  we 
may  allow  between  7  and  8  parts  carbonic  acid  gas  per  10,000  at 
the  end  of  the  period  of  occupancy,  inasmuch  as  they  are  crowded 
•only  on  rare  occasions,  and  are  also  assumed  to  be  thoroughly  ven- 
tilated before  occupancy,  as  of  course  should  be  the  case,  the  pro- 
portion of  carbonic  acid  gas  reaching  the  maximum  only  toward 
the  end  of  the  occupancy  period.  In  schools  and  hospitals  we 
-should  never  allow  over  6  parts  in  10,000,  and  as  these  are  occu- 
pied for  long  periods  fully  3,000  cubic  feet  of  air  should  be  allowed 
per  person  per  hour,  and  in  many  hospitals,  on  account  of  the 
•condition  of  the  occupants,  much  more.  Churches,  theaters  and 
lecture  rooms,  besides  being  occupied  by  a  variable  number,  are 
occupied  for  from  one  to  three  hours  at  a  time,  while  libraries  and 
reading  rooms  may  be  said  to  be  occupied  continuously. 

An  inspection  of  the  table  and  formulas  already  given,  with 
proper  allowance  for  the  considerations  here  cited,  will  warrant 
the  use  of  Table  No.  2. 

TABLE  NO.  2.— AMOUNT  OF  AIR  TO  BE  SUPPLIED  PER  PERSON  PER 
HOUR  IN  BUILDINGS   OF  VARIOUS   KINDS. 

Hospitals   3,600  to  5,000  cu.  ft.  per  hour 

Barracks    3,000  cu.  ft.  per  hour 

Schools 2,500  to  3,000  cu.  ft.  per  hour 

Libraries  based  on  crowded  capacity 2,000  cu.  ft.  per  nour 

Reading  rooms  based  on  crowded  capacity 2,200  cu.  ft.  per  hour 

Churches  based  on  crowded  capacity 1,400  cu.  ft.  per  hour 

Lecture  rooms  based  on  crowded  capacity 1,500  cu.  ft.  per  hour 

'Theaters  based  on  crowded  capacity 1,400  cu.  ft.  per  hour 

For  the  latter,  based  on  maximum  seating  capacity  : 

Churches 1,400  cu.  ft.  per  hour 

Lecture  rooms  1,800  cu.  ft.  per  hour 

Theaters 1,600  to  1,800  cu.  ft.  per  hour 


102  STEAM  HEATING  AND  VENTILATION. 

No  room  which  is  occupied  for  more  than  five  hours  continuously 
by  a  definite  number  of  adults  is  adequately  ventilated  with  a  less, 
allowance  than  2,400  cubic  feet  per  hour  per  individual,  and  3,000 
should  be  given. 


CHAPTEE  VIII.— SYSTEMS  OF  MECHANICAL  VENTILA- 
TION. 

In  the  last  chapter  were  discussed  the  general  principles  on 
which  depend  the  volume  of  air  necessary  to  give  good  ventilation ; 
the  next  point  for  consideration  is  the  method  by  which  this  air 
is  to  be  supplied  and  distributed.  In  the  earlier  days  of  me- 
chanical ventilation  two  general  systems  of  air  distribution  were 
considered,  the  plenum  or  pressure  system,  and  the  exhaust  sys- 
tem. In  the  former  the  fresh  air  is  drawn  from  the  outside  and 
forced  by  the  fans  into  the  rooms  to  be  ventilated,  and  finds  its 
way  out  again  through  flues  provided  for  t  e  purpose.  In  the  ex- 
haust system,  flues  or  ducts  are  provided  for  the  inlet  of  the  air, 
but  the  fans  are  connected  to  the  outlets  and  the  circulation  of 
air  is  maintained  by  drawing  out  the  vitiated  air  and  allowing  the 
fresh  air  to  take  its  place. 

The  plenum  system  is  generally  considered  more  direct  and  posi- 
tive, but  this  idea  arises  largely  from  the  fact  that  when  the  ex- 
haust system  has  been  used  alone  the  fans  are  connected  to  flues  in 
the  top  of  the  room,  and  the  inlets,  if  provided  at  all,  are  small  and 
poorly  located,  so  that  most  of  the  incoming  air  comes  from  doors 
and  windows  and  passes  out  of  the  flue  without  coming  much  in 
contact  with  the  occupants.  Theoretically,  either  system  is  effi- 
cient if  it  is  properly  designed  and  arranged,  but  the  best  results 
are,  generally  obtained  in  practice,  especially  for  large  halls  or 
rooms,  by  a  combination  of  both  systems.  Some  years  ago  many 
rooms  were  ventilated  on  the  principle  that  if  a  sufficient  quantity 
of  fresh  air  were  forced  into  a  room,  it  could  find  its  way  out 
through  doors  and  windows.  This  was  soon  found  to  be  a  mis- 
take, as  in  winter  all  windows  and  doors  would  be  closed  on  ac- 
count of  cold  and  the  outside  winds ;  and  it  is  impossible  to  force  air 
into  a  room  unless  an  adequate  outlet  is  provided. 

In  the  opinion  of  the  author,  the  distribution  of  the  air  supply  is 
even  more  important  to  the  success  of  a  ventilating  system  than 
the  volume,  and  there  is  much  that  might  be  written  on  what  not 
to  do.  It  is  difficult  to  lay  down  general  rules,  as  each  separate 


104  STEAM  HEATING  AND  VENTILATION. 

ease  requires  careful  study,  with  proper  consideration  of  the  local 
conditions.  The  use  to  which  the  room  is  to  be  put,  the  arrange- 
ment of  the  occupants  (whether  the  seats  are  fixed  or  movable), 
the  duration  of  occupancy,  the  method  of  heating,  the  kind  and 
extent  of  the  outside  exposure  and  the  height  of  the  room  must 
all  be  taken  carefully  into  account  in  determining  the  location  of 
inlets  and  outlets.  The  point  that  must  be  borne  constantly  in 
mind  is  that  the  most  perfect  ventilation  is  desired  not  at  the 
top  of  the  room,  or  along  the  floor,  but  at  the  breathing  line,  which, 
as  a  rule,  is  about  4  feet  above  the  floor  level.  There  are  very 
many  rooms,  unfortunately,  which  are  much  better  ventilated  at 
the  ceiling  than  at  the  breathing  line. 

Upward  versus  downward  ventilation. — There  is  one  question 
which  enters  more  or  less  into  every  problem  of  ventilation,  but 
especially  into  that  of  theaters,  churches  and  other  large  halls, 
which  is  a  source  of  continual  and  arduous  discussion  among  archi- 
tects and  ventilating  engineers — that  is,  the  respective  value  and 
merits  of  upward  and  downward  ventilation,  the  former  referring 
to  supplying  the  fresh  air  at  the  floor  and  drawing  the  vitiated  air 
out  at  the  top,  and  the  latter  to  the  reverse  of  this  method.  The 
upward  method  is  decidedly  the  natural  one,  as  the  temperature 
of  the  air  is  normally  about  30  degrees  lower  than  the  temperature 
of  the  body,  and  the  latter  gives  off  enough  heat  when  in  repose  to 
raise  the  temperature  of  1,800  cubic  feet  of  air  per  hour  10  de- 
grees. A  person,  therefore,  standing  in  an  open  space,  creates 
an  upward  current  which  naturally  carries  the  exhalations  from 
the  body  away  from  it.  The  downward  method  of  ventilation  must 
necessarily  be  opposed  to  the  tendency  of  the  individual  currents 
from  the  bodies  of  the  occupants  of  the  room,  and  carries  the 
breath  back  upon  them,  requiring  a  larger  volume  of  incoming  air 
to  effect  proper  dilution  than  the  upward  method. 

In  rooms  which  are  heated  entirely  by  the  incoming  air,  the 
temperature  of  the  latter  is  frequently  much  higher  than  the  aver- 
age temperature  near  the  occupants,  and  in  cold  weather  is  fre- 
quently higher  than  that  of  the  body.  In  this  case  the  air  loses 
its  heat,  as  the  air  descends,  and  to  a  large  extent  the  natural  cir- 
culation is  downward.  But  in  such  cases  the  chief  loss  of  heat  is 
due  to  outside  walls  and  windows,  and  the  consequence  is  that 
there  is  a  strong  current  downward  at  the  windows,  and  along 
the  floor  to  the  outlets,  while  a  large  part  of  the  breathing  line 


STEAM  HEATING  AND  VENTILATION.  105 

•escapes  with  what  ventilation  conies  from  a  meager  degree  of  dif- 
fusion. Prof.  S.  H.  Woodbridge,  in  his  admirable  report  to  the 
Committee  on  Rules  of  the  United  States  Senate  (rendered  De- 
cember 14,  1895),  on  the  Heating  and  Ventilation  of  the  Senate 
Wing  of  the  United  States  Capitol  at  Washington,  has  an  interest- 
ing discussion  of  this  subject,  especially  in  reference  to  large  halls, 
and  contains  the  following  summary  of  his  views  upon  the  sub- 
ject : 

"Especially  when  the  walls  of  the  auditorium  are  inside  walls 
and  warm,  the  air  supply  does  not  then  have  to  carry  surplus  heat 
to  compensate  for  loss  through  cold  outer  walls  and  windows.  It 
must  generally  enter  the  room  cooler  than  the  air  of  the  room  be- 
cause of  the  animal  furnaces  within  it,  each  occupied  chair  repre- 
senting approximately  the  heating  effect  of  a  burning  candle.  In 
legislative  halls  the  temperature  of  the  air  supplied  is  generally 
from  2  to  5  degrees  lower  than  the  air  of  the  room.  In  crowded 
auditoriums,  as  theaters,  the  temperature  of  the  supply  has  been 
known  to  have  been  held  for  hours  from  10  to  15  degrees  lower 
than  the  auditorium  temperature,  the  per  capita  hourly  supply 
being  in  excess  of  1,200  cubic  feet. 

"When  air  cooler  than  the  air  of  a  room  enters  it  in  large  quan- 
tities, the  most  rational,  as  also  the  safest,  way  of  admitting  it  is 
in  a  quiet  and  well-diffused  manner  through  the  floor.  It  then 
finds  itself  in  its  natural  position  of  stable  equilibrium.  Because 
cooler,  it  is  also  heavier  than  the  air  of  the  warmer  room,  and  it 
is  at  once  in  its  normal  position  at  the  floor,  where  it  envelops  the 
breather,  or  is  ready  for  easy,  short  and  direct  movement  to  the 
user.  The  warmer  and  polluted  air  is  above,  and  in  its  own  natural 
position  or  stable  equilibrium,  and  ready  for  the  shortest  and 
•easiest  escape  through  the  ceiling  vent. 

"Ventilation  by  removal  is  the  most  perfect  of  all  methods,  both 
in  the  completeness  of  its  work  and  in  the  economy  of  its  opera- 
tion. The  nearest  possible  approach  in  practice  to  ventilation  of 
occupied  rooms  by  the  removal  method  is  found  when  one  is  sur- 
rounded by  cool,  pure,  quiet  and  abundant  air  which  the  heat  of 
the  body  can  freely  move  in  an  approaching  and  enveloping  and 
ascending  current  about  and  from  the  body.  That  is  upward  ven- 
tilation. If  the  conditions  are  reversed,  the  fresh  air  entering 
at  the  ceiling  and  the  spent  being  withdrawn  at  the  floor,  the  fol- 
lowing results  seem  inevitable : 


106 


STEAM  HEATING  AND  VENTILATION. 


STEAM  HEATING  AND  VENTILATION.  107 

"First,  the  entering  air  being  cooler  and  more  dense  than  that 
within  the  room,  it  must  be  entered  in  greatly  diffused  form  to 
escape  the  production  of  drafts,  since  its  weight  must  cause  its 
precipitation ;  and  if  it  falls  either  by  the  swooping  down  en  masse, 
now  here  and  now  there,  or  by  continuous  flow  from  large  and 
scattered  wall  or  ceiling  inlets,  the  effects  will  vary  from  the  an- 
noying to  the  intolerable,  according  to  the  momentary  or  continu- 
ous action  of  such  down-flowing  drafts.  The  condition  of  stable 
equilibrium  is  reversed  by  such  a  procedure,  and  nature's  effort 
to  restore  that  equilibrium  must  necessarily  result  in  disturbance. 

"Second,  the  mass  movement  of  air  being  downward,  is  in  direct 
conflict  with  the  individual  currents,  which  are  upward.  The  indi- 
vidual currents  rise,  as  may  be  shown  by  experiment,  and  as  may 
be  also  seen  by  the  ascent  of  smoke  entangled  in  the  breath,  with 
a  movement  varying  from  20  to  40  feet  per  minute.  To  turn  these 
individual  currents  downward,  and  to  insure  their  moving  from 
the  nostrils  and  body  floorward  would  require  a  mass  downward 
movement  of  the  air  over  the  entire  area  of  the  Chamber  of  about 
30  feet  per  minute,  which  would  be  equivalent  to  a  per-minute 
supply  for  the  floor  alone  of  129,000  cubic  feet  of  air.  The  ascend- 
ing individual  currents  average  from  40  to  50  cubic  feet  per  min- 
ute, under  favorable  conditions  of  supply  of  fresh  air  to  the  body, 
and  of  rise  of  vitiating  air  from  it.  To  completely  reverse  this  air 
flow,  about  twenty-five  times  such  quantities  in  mass  movement 
would  be  required. 

"Unless  such  a  complete  reversal  is  effected,  the  occupant  must, 
in  downward  ventilation,  breathe  air  which  contains  his  own  and 
others  exha1  1  breath  and  dermal  vapors  turned  back  upon  him. 
He  is  in  the  p^Jtion  of  a  candle  burning  at  the  bottom  of  an  open 
pipe  through  which  the  air  current  is  being  unnaturally  forced 
downward.  He  is  at  the  discharge  end  of  the  ventilating  system 
rather  than  at  the  supply  end.  He  is  breathing  a  dilution  of  com- 
posite eliminations.  The  effect  on  gas  flames  distributed  and 
burning  at  the  floor  of  a  chamber,  to  which  the  controlled  air 
supply  was  admitted  in  diffused  form,  showed  that  by  the  down- 
ward method  of  supply  the  luminosity  of  flame  is  less  than  5  per 
cent,  of  that  obtained  when  the  same  air  quantity  is  used  with 
upward  ventilation,  the  quantity  of  air  used  being  a  little  more 
than  sufficient  to  bring  the  flames  to  a  maximum  luminosity  by  up- 
ward ventilation.  The  life  of  the  flame  seemed  even  then  to  de- 


108 


STEAM  HEATING  AND  VENTILATION. 


pend  on  the  local  down  drafts  of  fresh  and  cool  air,  which  was 
denied  admission  at  the  bottom  of  the  Chamber,  the  place  of  its 
natural  entrance. 

"Upward  movement  makes  necessary  the  use  of  only  enough 
air  to  supply  the  individual  upward  currents,  in  order  to  envelop 
the  occupant  in  the  purest  air  it  is  possible  to  provide  by  artificial 
ventilation  methods.  In  crowded  theaters  it  has  recently  been 
found  that  with  a  well-diffused  air  supply  of  1,200  cubic  feet  per 
capita  per  hour  the  air  below  the  breathing  line  can  be  kept  with- 
in 1  part  in  10,000  of  carbonic-acid  increment. 


F'O-58  U    F.G.59 

THC  EMGMtcnt 

Types  of  Diffusers  for  Theaters. 

"The  contrast  between  results  of  upward  and  downward  audi- 
torium ventilation  with  equal  air  quantities  can  perhaps  be  best 
imagined  by  considering  the  effects  on  a  theater  floor  crowded 
with  smokers. 

"Third.  In  the  case  of  the  Senate  Chamber,  the  galleries,  fre- 
quently occupied  with  persons  of  varying  degrees  of  cleanliness, 
become  an  important  factor.  To  so  ventilate  as  to  carry  the  gal- 
lery air  downward  through  the  Chamber  floor  would  be  a  piece  of 
professional  malpractice. 


STEAM  HEATING  AND   VENTILATION.  10i> 

"The  only  logical  reason  to  be  advanced  in  favor  of  downward 
ventilation  is  cleanliness;  that  is,  if  the  air  passages  of  the  floor 
are  foul,  then  downward  ventilation  does  not  bring  a  contamina- 
tion due  to  that  foulness  into  the  Chamber.  Practically,  however, 
it  is  exchanging  a  seen  and  relatively  harmless  offense  for  the  un- 
seen menaces  of  vitiated  airs.  Moreover,  the  only  vestige  of  a 
reason  for  downward  ventilation  disappears  when  air  is  draftlessly 
moved  through  the  floor  and  through  channels  and  chambers  so 
constructed  and  cared  for  as  to  insure  cleanliness.  In  this  con- 
nection it  should  be  said  that  a  thorough  investigation  of  the 
supply  chambers  made  at  the  close  of  the  .last  Congress  and  before 
any  cleaning  had  been  done,  revealed  a  condition  of  cleanliness 
which  was  as  gratifying  as  it  was  surprising,  because  of  much  that 
has  been  said  and  also  because  of  my  own  preconceptions  to  the 
contrary." 

This  is  a  strong  argument  in  behalf  of  the  upward  system  for 
ventilating  halls  of  such  a  character.  In  the  writer's  opinion,  the 
argument  is  unassailable  and  the  success  of  Prof.  Woodbridge's 
work  in  the  Senate  Chamber  makes  it  especially  forceful.  The 
argument  that  is  frequently  made  against  the  upward  method  is 
that  it  is  difficult  to  secure  a  proper  distribution  of  the  incoming- 
air  without  causing  disagreeable  drafts  on  the  feet  and  legs  of 
the  occupants.  With  the  upward  system  the  inlets  must  be  dis- 
tributed among  the  seats,  since,  if  the  air  is  admitted  through 
large  registers  in  the  aisles,  it  ascends  straight  to  the  ceiling  with 
but  little  effect  on  the  occupants. 

Air  inlets  and  outlets. — When  the  air  is  admitted  by  small  open- 
ings under  the  seats  the  creation  of  drafts  is  difficult  to  avoid.  Dif- 
ficult it  is,  but  by  no  means  impossible.  The  inlets  must  be  so 
large  that  the  incoming  air  has  a  low  velocity  (not  over  150  feet, 
or  at  the  most  200  feet  per  minute)  and  so  arranged  that  the  air 
does  not  strike  directly  against  the  legs  of  the  occupants.  The 
trouble  in  most  cases  of  the  kind  is  that  the  inlets  are  not  nearly 
large  enough.  If  in  a  theater,  for  example,  we  are  going  to  have 
1,800  cubic  feet  per  person  per  hour,  and  this  is  to  come  in  at  a 
velocity  of  150  feet  per  minute,  it  will  be  seen  that  a  register 
about  6  inches  by  5  inches  or  2|  inches  by  48  inches  will  be  re- 
quired under  every  seat  in  the  house.  Furthermore,  this  inlet 
should  not  be  right  in  the  floor,  but  should  be  raised  up  a  few 
inches.  Figures  53,  54,  55  and  56  show  some  forms  of  "diffusers" 


110 


STEAM  HEATING  AND  VENTILATION. 


recommended  by  Prof.  Woodbridge  for  the  Senate  Chamber,  and 
Figures  57,  58  and  59  some  other  practical  forms  for  theaters. 
For  churches  it  is  easy  to  contrive  simple  forms  for  long  narrow 
inlets  along  the  pews.  It  will  be  seen  that  all  of  these  arrange- 
ments requires  that  the  inlets  be  connected  to  a  large  plenum  cham- 
ber underneath  or  that  the  arrangement  of  ducts  be  such  as  to  give 
a  perfectly  uniform  distribution  of  the  air  to  the  numerous  inlets. 


F.e.60 


Infet: 


Fio.61 


A  little  reflection  will  show  that  in  a  large  theater,  for  example, 
if  the  downward  ventilation  is  employed,  it  is  quite  as  necessary  to 
have  the  outlets  well  distributed  as  with  the  reverse  method.  The 
Chicago  Auditorium,  a  very  large  theater,  is  ventilated  on  this 
scheme.  The  outlets  are  under  the  seats,  but  are  small  and  not 
frequent.  The  consequence  is  that  most  of  the  air,  coming  down 
from  above,  goes  out  the  exits,  which  are  numerous,  and  the 
large  outlets  back  of  the  boxes,  leaving  a  pocket  in  the  middle  of 
the  house  which  frequently  becomes  very  close. 

For  smaller  rooms,  such  as  school  rooms,  small  churches,  lee- 


STEAM  HEATING  AND  VENTILATION. 


Ill 


ture  and  reading  rooms,  there  are  many  methods  of  air  distribution 
which  have  proved  successful  in  accomplishing  the  desired  result 
of  ventilating  along  the  breathing  line.  Figure  60  shows  a  method 
which  is  much  used  in  schoolhouses,  and  in  rooms  not  over  30  feet 

wide  it  is  very  suc- 
cessful. If  the  rooms 
are  of  much  greater 
width  there  should  be 
inlets  and  outlets  on 
both  sides.  Figure  61 
is  another  method 
much  used  in  school 
houses.  Figure  62  is 
a  very  practical  ar- 
rangement for  small 
churches,  but  it  obvi- 
ously requires  that, 
especially  in  winter, 
the  roof  and  windows 
be  very  tight.  These 
three  figures  show 
vertical  sections 
through  the  rooms. 

Figure  63  shows  a 
very  wasteful  method 
of  ventilation  which  is 
employed  in  the  read- 
ing rooms  of  a  large 
library.  Most  of  the 
air  in  this  case  (especi- 
ally in  mild  weather) 
goes  down  the  walls 
and  out  without  af- 
fecting the  breathing 
line.  An  improvement 
Figure  64.— Ventilation  in  a  Syracuse  Bank.  could  be  effected  by 

putting  inlets  at  the 

point  A.    There  is  always  a  tendency  of  air  currents  to  cling  to 

wall  surfaces  and  this  should  always  be  taken  into  consideration. 

Figure  64  shows  a  diagram  of  the  ventilation  of  the  large  bank- 


Plan. 


112  STEAM  HEATING  AND  VENTILATION. 

ing  room  of  the  Onondaga  County  Savings  Bank  at  Syracuse,  N.  Y. 
The  arrangement  is  very  successful,  and,  on  account  of  the  fact 
that  the  clerks  are  employed  at  the  windows  all  day  long,  may  be 
preferable  to  a  reversed  arrangement  of  inlets  and  outlets;  but 
with  the  system  employed,  the  air  supply  is  very  ample  in  propor- 
tion to  the  number  of  regular  occupants. 

Air  velocities  through  inlets  and  outlets. — As  to  the  size  of  inlets 
and  outlets  for  large  registers  for  ventilating  schemes  of  this  kind, 
standard  practice  allows  a  velocity  of  about  300  feet  per  minute 
through  the  gross  area  of  the  register.  Naturally  a  rule  of  this 
kind  is  dependent  upon  circumstances,  and  if  an  inlet  has  to  be 
where  air  will  blow  directly  on  any  of  the  occupants,  the  velocity 
should  be  slower.  Mr.  Wolff  states  that  when  air  enters  at  or  near 
the  floor,  the  velocity  should  not  exceed  120  feet  per  minute.  The 
author  has  taken  180  feet  per  minute  as  a  maximum  in  such  cases. 
This  figure  may  be  used  if  diffusers  are  arranged  so  that  the  air 
will  not  blow  directly  on  the  feet  and  ankles  of  the  occupants. 
Where  the  inlets  are  removed  from  the  danger  of  direct  drafts  on 
the  occupants,  a  velocity  of  300  feet  per  minute  may  be  used  with 
safety.  In  hospitals  and  similar  institutions,  the  inlets  and  out- 
lets should  be  very  carefully  placed  to  meet  the  requirements  of 
the  particular  arrangement  of  beds,  and  velocities  should  be  low. 
The  velocities  through  outlets  may  range  from  400  to  600  feet  per 
minute. 

There  is  another  consideration  which  should  be  discussed  at 
this  point,  as  it  seriously  affects  the  question  of  air  distribution. 
That  is  the  question  of  heating  by  means  of  the  ventilating  air.  In 
the  opinion  of  the  author,  this  is  never  desirable  in  a  room  of  what 
we  have  called  the  densely  peopled  character.  Especially  where 
there  is  any  considerable  amount  of  glass  or  exposed  wall  surface, 
there  should  be  heating  coils  in  the  room  sufficient  at  least  to 
counteract  the  loss  of  heat  from  such  surfaces;  otherwise  the  in- 
coming air  must  in  cold  weather  have  a  temperature  of  about  130 
degrees  or  more  and  is  very  hard  and  dry.  In  such  cases  the  inlets 
must  be  very  high,  so  as  not  to  be  near  the  occupants.  Besides 
this,  such  a  great  difference  in  temperature  between  the  incoming 
air  and  the  average  of  the  room  creates  currents  which  interfere 
with  the  uniform  circulation  desired,  in  addition  to  making  it  very 
difficult  to  maintain  a  uniform  temperature  throughout  the  room. 


CHAPTEE  IX.— VENTILATING  DUCTS. 

Theory  of  the  flow  of  air  in  ducts. — Any  flow  of  air  is  created  only 
by  an  inequality  in  the  pressure  of  the  air  at  two  different  points, 
and  it  follows  that  the  primary  requisites  for  a  ventilating  system 
are  a  means  for  creating  the  required  difference  in  pressure  and 
a  means  for  distributing  the  flow  of  air  to  required  points.  As 
accessory  to  the  first  of  these  there  is  generally  required  some 
means  for  heating  the  air  and  frequently  for  washing  it. 

The  theoretical  laws  which  govern  the  flow  of  air  are  very  dif- 
ficult of  direct  application  to  ventilating  conditions,  and  yet  a  clear 


FIG.  65 


FiQ.66     


Fio.67 


understanding  of  the  principles  governing  the  air  flow  is  necessary 
to  the  successful  understanding  of  the  way  in  which  air  can  be 
handled  in  a  ventilating  system. 

Consider  the  simplest  case :  a  pipe  or  duct,  AB,  Figure  65,  of  in- 
definite length,  in  which  a  flow  of  air  is  created  from  A  to  B.  This 
flow  can  only  be  kept  up  by  maintaining  the  air  pressure  at  A  in 
excess  of  that  at  B;  and  the  greater  this  excess,  the  greater  will 
be' 'the  velocity  of  air  in  the  duct.  Let  us  denote  this  excess,  or 
difference,  of  pressure  by  p.  It  can  be  measured  in  pounds  per 
square  inch,  ounces  per  square  inch  or  in  the  height  of  the  water 


114  STEAM  HEATING  AND  VENTILATION. 

column  which  it  will  balance.  In  ventilating  work,  since  p  is  gener- 
ally small,  it  is  measured  in  one  of  the  two  latter  units;  and  a 
column  of  water  1  inch  high  is  equivalent  to  0.579  ounce  per  square 
inch.  The  pressure  p  has  two  functions  to  perform;  it  must  create 
the  velocity  (v)  of  air  in  the  duct  and  it  must  overcome  the  fric- 
tional  resistance  to  the  passage  of  the  air.  X ow,  if  it  were  not  for 
the  friction  of  the  air  in  the  pipes,  the  velocity  could  be  expressed 
by  the  familiar  formula 

v=  1/Tgh 

in  which  v  is  given  in  feet  per  second  and  h  is  the  height  in  feet 
of  a  column  of  air,  the  weight  of  which  would  give  the  pressure  p 
which  creates  the  flow.  If  p  is  expressed  in  inches  of  water 
column,  h  =  [67.7  +  (t  -f-  520)]  p,  where  t  is  the  temperature  of 
the  air;  and  as  g  =  32  (approximately)  in  the  foot-pound-second 
fiystem  of  units,  the  formula  becomes: 

t  \ 

(1) 

As  already  stated,  this  represents  the  theoretical  velocity  that 
would  be  attained  if  there  were  no  frictional  resistance  to  be  over- 
come. This  formula  is  not  absolutely  accurate  even  for  the  theo- 
retical velocity  without  friction,  on  account  of  the  compressibility 
of  air,  but  with  the  pressures  attained  in  ventilating  plants,  the 
factor  of  correction  would  amount  to  a  very  small  fraction  of  1 
per  cent.  But  as  it  is,  the  actual  velocity  (v1)  may  be  anything 
irom  0.2  v  to  0.7  v,  and  under  the  conditions  of  most  ventilating 
plants  it  is  from  0.3  v  to  0.6  v.  Or,  v1  being  the  actual  velocity, 
we  may  put 


where  c  is  a  coefficient  which  will  vary  from  2.4  to  5  according  to 
the  nature  of  the  resistance  to  be  overcome,  its  maximum  value 
teing  8  for  the  theoretical  velocity  without  friction. 

Prof.  Unwin  gives  a  formula  for  the  flow  of  air  in  round  pipes 
which  is  as  follows  : 


=       / 

V 


T  d 


4ml  pos 

in  which  k  =  53.15;  T  =  absolute  temperature  of  air;  g  =  32.2; 


STEAM  HEATING  AND  VENTILATION.  115 

d  —  diameter  in  feet;  1  =  length  in  feet;  m  =  a  coefficient  of  fric- 
tion; p0  =  the  greater  absolute  pressure  and  px  =  the  lesser  press- 
ure. The  difficulty,  however,  with  any  such  formula  as  this  is  that 
in  any  ventilating  system  with  a  complicated  arrangement  of  ducts, 
containing,  as  it  must,  bends  and  branches,  dampers,  rectangular 
pipes  and  round,  registers,  heating  coils,  etc.,  it  is  beyond  the  pos- 
sibility of  theoretical  calculation  to  obtain  any  adequate  value  for 
•a  coefficient  of  friction. 

The  pressures  employed  in  ventilating  systems  do  not  usually 
exceed  1  ounce  per  square  inch,  nor  the  velocity  50  feet  per  sec- 
ond, or  3,000  feet  per  minute. 

The  accompanying  table  gives  the  velocity  v1  as  obtained  by 
formula  (2),  already  stated,  for  air  at  60  degrees  Fahr.  and 
various  values  of  c  and  different  pressures,  p.  This  table  is  rather 

TABLE  OF  AIR  VELOCITIES— TEMPERATURE   60  DEGREES  FAHR. 

., p x  , v1  in  feet  per  second * 

Inches  Oz.  per 

water.  sq.  in.  c  =  2.4  c  =  3.  c  =  4.  c  =  5. 

0.01  .006  2.0  2.5  3.3  4.1 

0.05  .030  4.4  5.6  7.4  9.2 

0.10  .058  6.2  7.8  10.4  13.0 

0.20  .116  8.8  11.0  14.6  18.4 

0.40  .232  12.5  15.6  20.8  26.0 

0.60  .347  15.1  18.8  25.2  31.5 

0.80  .463  17.4  21.8  29.2  36.4 

1.00  .579  20.0  25.0  33.  41.2 

2.00  1.158  28.2  34.8  46.4  57.8 

3.00  1.737  34.6  42.7  56.9  71.2 

4.00  2.316  40.  49.5  66.2  82.5 

difficult  to  apply  practically,  but  it  is  the  writer's  experience  thaj; 
in  a  well-proportioned  system  a  coefficient  of  5  can  be  used.  If 
the  ducts  are  very  long  or  tortuous,  or  contain  many  dampers,  a 
•smaller  one  should  be  used. 

It  will  be  seen  from  this  table,  as  well  as  from  formulas  (1),  (2) 
and  (3)  that  p  is  proportional  to  v2.  (In  formula  (3),  p0  —  px  is 
•equivalent  to  the  p  of  the  table  and  of  the  other  formulas,  and  for 
small  values  of  p,  p0  +  px  would  be  practically  a  constant.)  On  this 
account,  in  a  given  system  of  ventilating  ducts,  any  increase  in 
velocity  can  be  obtained  only  by  increasing  the  pressure  created 
by  the  fan,  proportionally  to  the  square  of  the  velocities.  And 
as  the  power  required  to  move  the  air  is  practically  proportional 
to  the  product  of  the  pressure,  area  and  velocity,  the  power  re- 
quired, exclusive  of  that  used  by  the  friction  of  fan  and  engine 
or  motor,  is  proportional  to  the  cube  of  the  velocity.  These  laws 


116  STEAM  HEATING  AND  VENTILATION. 

should  be  thoroughly  understood  by  all  who  have  anything  to  do- 
with  ventilating  systems.  They  would  be  still  more  important 
were  it  not  that  the  pressures  employed  in  ventilating  systems 
are  always  small,  rarely  exceeding  1  inch  of  water  column,  equal 
to  0.579  ounce  per  square  inch. 

Velocity  of  air  in  ducts. — From  what  has  been  said  it  may  be 
gathered  that  the  design  of  a  system  of  ventilating  ducts  is  largely 
a  matter  of  velocities.  The  velocity  in  the  main  ducts  may  vary 
from  30  to  65  feet  per  second,  the  latter  figure  being  somewhat 
excessive  if  the  ducts  are  of  any  considerable  length.  For  branch 
ducts  the  velocities  must  be  lower — the  smaller  the  duct  the  lower 
the  velocity — in  order  to  maintain'the  proper  distribution  through- 
out the  system.  This  seems  rather  indefinite,  and  so  it  is,  but 
there  is  no  branch  of  engineering  which  is  more  strictly  dependent 
upon  empirical  rules  and  the  experience  and  study  of  the  designer, 
than  the  design  of  a  ventilating  system.  We  may  take  35  to  40 
feet  per  second  as  a  standard  velocity  for  air  in  the  main  ducts, 
from  a  fan  delivering  from  20,000  to  40,000  cubic  feet  of  air  per 
minute.  In  the  branch  ducts  the  velocity  should  be  reduced,  ac- 
cording to  the  size  of  the  ducts,  as  low  as  20,  or  even  15  feet  per 
second  in  small  ducts  (8  x  10-inch  or  6  x  12-inch)  supplying  indi- 
vidual registers  in  small  rooms. 

The  velocity  through  the  registers  should  not  exceed  5  feet 
per  second  through  the  gross  area,  except  through  large  ones  so- 
located  that  there  is  no  possibility  of  a  direct  draft  on  the  occu- 
pants of  the  room.  If  these  proportions  are  carried  out,  the  neces- 
sary pressure  at  the  fan  to  force  air  through  the  ducts  will  not 
generally  exceed  0.3  ounce  per  square  inch,  but  it  must  be  borne  in- 
mind  that  additional  pressure  is  required  for  heating  coils  and 
other  similar  obstructions.  This  will  be  more  particularly  consid- 
ered in  a  subsequent  chapter.  The  pressure  necessary  will  in- 
crease rapidly  as  velocities  are  increased,  and  must  be  made  up  by 
increased  capacity  of  fans  and  increased  power. 

Branch  ducts. — In  laying  out  ducts  the  utmost  ingenuity  should 
be  exercised  in  arranging  the  branches,  dampers,  etc.  All  short 
bends  and  T-branches  should  be  carefully  avoided,  as  they  greatly 
reduce  the  flow  of  air.  A  frequent  specification  in  regard  to  bends 
is  that  the  inside  radius  of  the  bend  must  be  equal  to  the  diameter, 
or  equivalent,  of  the  pipe.  This  should  certainly  be  a  minimum 
and  twice  that  radius  would  be  a  preferable  minimum.  The  air 


STEAM  HEATING  AND  VENTILATION.  117 

-will  frequently  pass  right  by  a  right-angle  branch,  as  in  Figure 
G6.  The  velocity  in  the  branch  being  but  a  small  percentage  of 
that  in  the  main,  such  connections  should  be  made  as  in  Figure  67. 

Dampers. — Dampers  are  a  necessary  evil,  as  they  certainly  im- 
pede the  flow.  They  should  be  used  with  caution,  and  the  duct 
system  should  be  laid  out  in  the  first  place  with  as  few  dampers 
as  possible,  and  in  the  second  place  with  the  idea  that  under  nor- 
mal conditions  the  system  should  be  run  with  all  dampers  wide 
open. 

There  is  a  common  practice  when  laying  out  a  complicated  sys- 
tem of  ducts  with  numerous  branches  and  sub-branches  of  put- 
ting a  damper  on  every  branch,  the  idea  being  that  if  one  branch 
gets  more  than  its  share  of  air  it  can  be  "throttled  down"  by 
means  of  its  damper,  so  .that  the  other  branches  will  get  more. 
The  author  has  hardly  found  a  case  in  practice  where  dampers 
were  used  in  this  way  but  that,  in  the  course  of  practical  experi- 
ment on  the  part  of  an  ignorant  attendant  to  proportion  the  air 
supply,  most,  if  not  all,  of  the  dampers  were  more  or  less  closed, 
thus  diminishing  the  air  supply  and  throwing  a  greater  load  on 
the  fan.  It  is  not  alone  the  velocity  in  the  ducts  that  we  must 
look  after,  but  also  that  at  the  dampers;  a  few  half-closed  damp- 
ers will  have  a  decided  effect  upon  the  pressure  required  at  the 
fan. 

Dampers  should  only  be  put  in  at  or  near  the  registers,  and  in 
many  cases  the  system  is  better  off  without  them  even  there.  The 
branches  must  be  systematically  laid  out,  and  with  reasonable 
care  they  can  be  properly  proportioned  without  adding  dampers 
to  act  as  a  safeguard  on  the  designer. 

The  ordinary  butterfly  damper,  hung  by  the  rod  in  the  middle, 
is  the  type  most  employed.  They  should  be  firmly  attached  to 
the  rod,  so  that  they  cannot  work  loose.  The  damper  should  fit 
loose  in  its  duct  and  should  always  be  provided  with  a  substantial 
attachment  by  which  its  position  can  be  set  and  secured  from  the 
outside. 

Arrangement  of  ducts. — In  large  plants  the  ducts  usually  radiate 
from  the  fan  to  the  registers  in  a  tree-like  pattern;  but  in  the 
opinion  of  the  author,  although  apparently  the  simplest,  this  is 
in  reality  the  most  complicated  possible  way  to  lay  out  a  ventilat- 
ing system;  and  it  is  his  firm  opinion  that  much  better  results 
can  be  obtained  by  a  system  of  mains  and  feeders,  to  borrow  elec-1 


118 


STEAM  HEATING  AND  VENTILATION. 


trical  phraseology.  The  idea  of  the  first  system  is  indicated  in 
Figure  68,  and  that  of  the  second  in  Figure  69.  The  diagram  in 
each  case  represents  the  basement  of  a  building,  VW  being  ver- 
tical flues  which  it  is  necessary  to  supply  with  air.  In  Figure  69 
M  may  be  called  the  mains  and  F  the  feeders.  In  the  "tree"  sys- 
tem of  Figr.re  68  it  is  difficult  indeed  to  prevent  the  ducts  near- 
est the  fan  ifrom  taking  most  of  the  air,  and  a  much  more  uniform 
distribution  is  obtained  by  the  other  system,  especially  if  the  mains 
are  made  large  so  that  the  velocity  is  low.  The  feeders  can  then. 


ENGINEERING  RECORD. 


Types  of  Duct  Arrangement. 


be  proportioned  for  a  comparatively  high  velocity  (45  to  60  feet 
per  second  for  large  systems)  without  loss.  The  connection  to 
the  vertical  flues  should,  of  course,  be  curved  upward  from  the 
mains,  or  the  connection  made  very  free.  In  this  system  the 
object  is  to  make  the  mains  something  of  a  plenum  chamber  in 
which  the  velocity  is  slow  and  the  pressure  uniform  throughout. 

In  a  large  system,  where  several  fans  are  used,  the  best  results 
will  be  obtained  by  locating  two  or  three  plenum  chambers,  as 
mains  or  as  centers  of  distribution,  at  central  points,  from  which 


STEAM  HEATING  AND  VENTILATION.  119 

the  ducts  can  radiate,  and  to  each  of  which  feeders  from  the 
fans  can  be  conducted. 

A  large  library  building  in  the  Middle  West  is  a  case  in  point.  It 
is  ventilated  by  an  elaborate  system  with  five  large  supply  fans  and 
as  many  exhaust  fans.  The  ducts  radiate  from  the  fans  on  the 
"tree"  system,  each  fan  connecting  to  its  own  independent  system 
of  ducts.  The  ducts  are  large  and  long  and  ramify  through  the 
basement  so  as  to  render  useless  a  large  amount  of  valuable  space. 
As  the  system  stands,  it  is  very  difficult  to  adjust  the  air  supply 
to  the  different  ducts  and  the  pressures  on  the  different  fans  are 
very  unequal.  If  two  plenum  chambers  had  been  located  in  the 
center  of  each  end  of  the  building  and  each  of  the  supply  fans 
connected  into  one  or  the  other,  it  would  have  greatly  simplified 
the  air  distribution,  taken  up  much  less  space  and  equalized  the 
pressure  and  the  load  on  the  different  fans,  some  of  which  at 
present  are  considerably  overloaded,  while  others  are  the  reverse. 

Figure  70  shows  the  basement  plan  of  a  building  taken  from 
The  Engineering  Eecord.  The  following  description  of  the  ar- 
rangement of  ducts  accompanied  the  plan:  Fresh  air  enters 
through  windows  at  the  northeast  corner  of  the  basement,  where 
the  fan  is  located.  In  cold  weather  the  air  passes  through  the 
windows  of  a  tempering  chamber  provided  with  tempering  coils,, 
but  in  moderate  weather  this  chamber  is  shut  off  and  windows  in. 
the  fan  room  adjoining  are  opened  to  allow  the  air  to  pass  di- 
rectly to  the  fan.  By  means  of  an  8-foot  blower  the  air  is  de- 
livered into  a  plenum  chamber  about  10  x  17  feet  in  size  adjoin- 
ing the  fan  room.  From  this  the  air  is  forced  to  three  indirect 
heating  chambers,  constructed  of  brick,  located  at  convenient 
points  in  the  basement,  from  which  both  heated  and  tempered 
air  may  be  uniformly  distributed  by  the  double  duct  system  to 
the  base  of  the  heat  flues.  One  of  these  heating  chambers  is  built 
within  the  plenum  chamber,  while  the  other  two  are  located  at, 
distant  points  and  connected  with  it  by  galvanized-iron  ducts.. 
The  heating  chambers  are  numbered  1,  2  and  3  in  the  drawing.. 
Number  1  is  located  inside  of  the  main  plenum,  while  the  other- 
two  are  located  at  distant  points  of  the  basement,  as  shown. 

It  will  be  seen  that  in  this  plant  the  vertical  ducts  are  sup- 
plied from  the  three  chambers,  which  are  practically  three  centers 
of  distribution,  but,  in  the  opinion  of  the  author,  the  system  could 
have  been  improved  by  locating  four  main  ducts  at  M,  N,  0,  P,  and 


120 


STEAM  HEATING  AND  VENTILATION. 


STEAM  HEATING  AND  VENTILATION. 


121 


supplying  these  by  feeders  from  the  fan  at  points  about  at  the 
middle  of  the  mains.  The  four  mains  would  supply  the  vertical 
flues  in  the  four  sections  of  the  building  and  they  could  be  con- 
nected together  by  a  small  equalizing  duct  forming  a  sort  of  ring 
system  around  the  building.  Of  course  there  may  be  objections 
to  such  a  system  on  account  of  the  constructional  features  of  the 
building,  or  the  special  use  of  certain  rooms,  and  in  the  case  un- 
der consideration  the  engineer  wished  to  place  a  heating  coil 
in  each  of  his  centers  of  distribution;  but  this  being  the  case,  it 
would  have  been  better  to  locate  four  centers  of  distribution;  for 
example,  at  D,  E,  F  and  G,  the  object  being  to  make  the  connec- 
tions from  them  to  the  vertical  flues  as  short  and  direct  as  pos- 
sible. In  this  case  they  should  each  have  a  feeder  from  the  fan 
and  could  be  profitably  connected  by  an  equalizing  duct  from 
which  the  stray  vertical  ducts  between  them  could  be 
connected.  The  question  of  the  distribution  of  heat- 
ing coils  in  ducts  will  be  further  considered  in  a 
subsequent  chapter.  Figure  72  represents  another 
building  in  which  three  centers  could  have  been 
very  advantageously  located  at  A,  B  and  C.  The 
ducts  shown,  it  may  be  pointed  out,  form  the  ex- 
haust system  of  a  downward  ventilating  apparatus 
installed  in  this  building. 

In  regard  to  vertical  flues,  they  should,  if  possible, 
be  separate  for  each  outlet;  and  the  longer  the  duct, 
the  slower  the  velocity  to  be  allowed.  The  author 
is  familiar  with  one  building  in  which  some  of  the 
vertical  flues  supply  three  registers.  Each  outlet  is  provided 
with  an  adjustable  swing  damper,  as  indicated  in  Figure  71,  and 
it  is  exceedingly  difficult  to  adjust  them  so  as  to  give  anything 
like  a  uniform  distribution  to  the  three  outlets. 

Materials  for  ducts. — As  to  the  material  for  the  construction  of 
ducts,  they  are  usually  made  of  galvanized  iron,  in  which  case  they 
should  be  soldered  at  the  joints,  as  it  is  very  essential  that  they 
be  made  air  tight.  Large  ducts  are  frequently  made  of  sheet  iron, 
and  these  should  be  close  riveted;  and  when  they  are  painted,  the 
joints  should  be  thoroughly  doped  with  an  asphalt  or  other  simi- 
lar paint. 

Underground  ducts  should  be  made  of  brick.  Wood  is  objec- 
tionable in  any  case,  and  especially  so  unless  the  ground  is  very 


Fie.71 


V 


V 


122 


STEAM  HEATING  AVZ)  VENTILATION. 


STEAM  HEATING  AND   VENTILATION.  123 

dry,  and  they  should  be  lined  with  tin  or  galvanized  iron  to  make 
them  tight.  Brick  ducts  should  be  plastered  inside  and  out  all 
around  with  a  f-inch  coat  of  rich  cement  mortar,  or,  preferably, 
asphalt.  There  is,  among  some  engineers,  but  more  particularly 
among  ventilating  contractors,  an  opposition  to  underground 
ducts.  The  author  has  thought  this  originated  with  the  latter 
largely  from  the  fact  that  there  is  less  profit  for  the  ordinary  ven- 
tilating contractor  in  building  brick  ducts  than  there  is  in  iron. 
The  objection  is  raised  that  they  are  liable  to  become  damp  and 
dirty.  This  is  not  at  all  the  case  if  they  are  properly  made.  In 
fact,  from  the  standpoint  of  cleanliness,  they  are  preferable  to 
iron,  as  any  duct  will  become  very  dirty  in  time,  and  brick  ones 
can  be  easily  arranged  so  as  to  be  washed  out  with  a  water  stream 
from  a  hose.  Underground  ducts  must,  of  course,  as  a  rule,  be 
laid  out  before  the  building  is  built,  and  it  is  not  generally  prac- 
ticable to  put  very  small  ones  underground;  but  with  a  system 
designed  with  centers  of  distribution  and  feeder  ducts,  as  sug- 
gested, the  latter  could,  in  most  cases,  be  put  underground  with 
great  advantage.  In  the  building  first  referred  to,  not  only  the 
feeder  ducts,  but  the  centers  of  distribution  as  well,  might  have 
been  put  underground,  and  at  less  expense  than  the  existing  sys- 
tem, if  the  work  had  been  laid  out  at  the  proper  time.  There 
is  an  objection  to  blowing  heated  air  through  underground  ducts, 
but  this  will  be  considered  in  the  following  chapter. 


CHAPTEE  X.— VENTILATING  FANS  AND  OTHEE  APPA- 

EATUS. 

Types  of  fans. — There  are  but  two  kinds  of  fans  commonly  used 
in  ventilating  plants.  These  are  the  centrifugal  fan,  or  blower, 
and  the  propeller,,  or  disk  fan.  The  distinctive  characteristics  of 
the  two  types  are  well  shown  in  Figures  73  and  74. 


Figure  73.— The  Centrifugal  Fan. 


The  centrifugal  fan  consists  of  a  wheel  with  several  vanes 
mounted  on  a  horizontal  shaft,  as  shown  in  Figure  75,  where  the 
covering  or  casing  is  removed.  It  is  always  mounted  in  this  cas- 
ing, which  may  be  of  wood,  brick  or  iron,  but  usually  the  last, 
although  for  large  fans  the  bottom  part  is  generally  of  brickwork 
and  the  top  of  iron.  The  air  enters  through  an  opening  in  the 


STEAM  HEATING  AND  VENTILATION. 


125 


center  and  is  forced  to  the  outlet  by  the  centrifugal  action  due  to 
the  rapid  revolution  of  the  fan  wheel. 

The  disk  fan  is  mounted  in  an  opening  in  a  wall,  or  in  the  end 
of  a  pipe,  and  drives  air  by  means  of  its  screw-like  action.  The 
disk  fan  is  only  used  against  very  light  pressures,  and  consequent- 
ly, when  ducts  are  very  short  and  openings  large  and  few,  the  disk 
fan  loses  in  efficiency  rapidly  as  the  pressure  rises. 

Centrifugal  fan  capacities. — There  is  no  manufactured  machine 
about  which  there  are  so  many  varying  data  as  there  is  in  connec- 


Figure  74.— The  Disk  Fan. 

tion  with  ventilating  fans.  The  makers'  claims  as  to  capacity  are 
generally  too  high. 

Mr.  Alfred  E.  Wolff,  in  his  very  excellent  pamphlet  on  "The 
Ventilation  of  Buildings,"  publishes  the  accompanying  table,  Ta- 
ble I,  for  centrifugal  fans.  This  table,  like  everything  else  from 
Mr.  Wolff's  pen  on  the  subject,  is  very  valuable,  although  the  ex- 
perience of  the  author  in  testing  some  large  fans  would  indicate 
that  even  the  capacities  here  given  are  somewhat  too  liberal. 

Mr.  M.  C.  Huyett,  an  ex-fan  manufacturer  of  extended  experi- 
ence, has  published  a  valuable  table  of  centrifugal  fan  capacities 
which  is  given  in  Table  II.  Mr.  Huyett's  table  is  based  on  the 


126 


STEAM  HEATING  AND  VENTILATION. 


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f  STEAM  HEATING  AND  VENTILATION.  127 

velocity  of  the  fan-wheel  periphery  multiplied  by  the  "blast  area" 
of  the  fan.  The  blast  area  being  practically  the  area  of  the  blade, 
is  taken  as  the  width  of  the  wheel  multiplied  by  one-third  of  the 
diameter.  As  Mr.  Huyett  points  out,  it  will  be  seen  that  this  rep- 
lesents  a  maximum  velocity  for  the  air,  as  it  is  impossible  to  give 
to  it  a  velocity  greater  than  that  of  the  wheel  rim.  The  table 
may,  therefore,  be  taken  as  representing  practically  a  free  air 
discharge,  and  checks  very  close  with  the  author's  tests  made  on 
fans  working  under  low  velocities  or  free  delivery  in  the  ducts. 

TABLE  I.— QUANTITY  OP  AIR  SUPPLIED  BY  BLOWERS  OF  VARIOUS 

SIZES  AGAINST  A  PRESSURE  OF  ONE  OUNCE  PER  SQUARE 

INCH.      (ALFRED    R.    WOLFF.) 


Diam. 

Revs,  per 

H.-P.  to 

Cubic  ft. 

wheel,  ft. 

minute. 

drive  blower. 

per  minute. 

4 

350 

6. 

10,635 

5 

325 

9.4 

17,000 

6 

275 

13.5 

29,618 

7 

230 

18.4 

42,700 

8 

200 

24. 

46,000 

9 

175 

29. 

56,800 

10 

160 

35.5 

70,340 

12 

130 

49.5 

102,000 

14 

110 

66. 

139,000 

15 

100 

77. 

160,000 

The  theoretical  calculation  of  fan  discharge  is  very  compli- 
cated, and,  so  far  as  the  author's  experience  goes,  is  very  unreliable 
on  account  of  the  difficulty  of  obtaining  accurate  values  for  the 
coefficients. 

In  a  paper  in  the  "Transactions"  of  the  American  Society  of 
Heating  &  Ventilating  Engineers,  for  1899,  Prof.  R.  C.  Car- 
penter deduces  a  formula  in  which  the  fan  "capacity  is  equal  to 
the  product  of  three  constants  multiplied  by  the  width  of  wheel, 
diameter  of  inlet,  and  by  diameter  of  fan  wheel  into  the  number 
of  revolutions."  He  states  also  that  since,  by  common  practice 
the  three  first  factors  are  now  always  made  proportional  to  one 
•another,  the  formula  becomes 

q  =  c  n  d3, 

by  which  q  is  obtained  as  cubic  feet  per  minute,  d  being  the  diame- 
ter in  feet  of  the  fan  wheel,  n  the  number  of  revolutions  per  min- 
ute, and  c  a  coefficient,  the  value  of  which  Prof.  Carpenter  gives 
as  0.6  for  single-inlet  fans  under  free  discharge,  0.5  with  a  press- 
ure of  1  inch  of  water,  and  0.4  with  a  pressure  of  1  ounce  per 
square  inch.  "For  fans  with  double  inlets  the  coefficient  should 
be  increased  50  per  cent."  For  practical  work  on  ventilating 


128 


STEAM  HEATING  AND  VENTILATION. 


plants  Prof.  Carpenter  recommends  c  =  0.4.  This  coefficient 
gives  capacities  which  are  about  10  per  cent,  less  than  those  of 
Mr.  Wolff's  table,  and  is  very  reliable  where  duct  velocities  are 
employed  such  as  the  author  recommends  in  the  preceding  chap- 
ter, with  45  to  55  feet  per  second  in  the  main  duct;  but  where 
heating  coils  and  other  similar  resistance  are  interposed  in  the 
air  passages,  as  is  generally  the  case,  a  coefficient  of  c  =  0.35  is 
much  safer. 

Prof.  Carpenter  also  gives  a  formula  for  the  power  required  to 
drive  centrifugal  fans  ("Transactions"  Am.  Soc.  Htg.  &  Vent. 
Engrs.,  Vol.  V.,  p.  237),  which  is: 

HP  =  b  d5  n3  -T-  106, 
in  which  H  P  is  horse-power  delivered  to  the  fan;  d,  the  diameter 


Figure  75.— Centrifugal  Blast  Wheel. 

in  feet;  n,  the  number  of  revolutions  per  second,  and  b  a  coeffi- 
cient, which  should  be  taken  as  30  for  free  delivery  and  20  for  de- 
livery against  1  ounce  pressure.  This  formula,  with  a  coefficient 
of  20,  gives  results  almost  identical  with  those  of  Mr.  Wolff's 
table,  and  may  be  taken  as  very  reliable  for  practical  work.  It  is. 
interesting  to  note  that  according  to  Prof.  Carpenter's  coefficient,, 
the  power  required  for  free  delivery  is  50  per  cent,  greater  than 
when  working  against  a  pressure  of  1  ounce.  This  is  in  accord- 
ance with  experience,  as  well  as  theory,  but  is,  of  course,  due  to 
the  fact  that  the  volume  of  air  delivered  under  free  discharge 
is  much  greater  than  under  1  ounce  pressure. 

Disk  fans. — Disk  fans,  as  stated  above,  are  not  generally  used 


Diam. 

Revs,  per 

H.-P.  to 

wheel,  ft. 

minute. 

drive  fan. 

2.0 

600 

0.50 

2.5 

550 

0.75 

3.0 

500 

1.00 

3.5 

500 

2.50 

4.0 

475 

3.50 

5.0 

350 

4.50 

6.0 

300 

7.00 

7.0 

250 

9.00 

STEAM  HEATING  AND  VENTILATION.  129 

where  large  capacity  is  required,  except  where  the  delivery  is  very 
free.  They  are  usually  employed  where  exhaust  fans  are  required 
on  roofs,  or  in  other  elevated  positions  where  it  is  impracticable 
to  set  the  large  foundation  which  the  centrifugal  fan  requires.  It 
is  the  opinion  of  the  author  that  the  field  of  usefulness  of  the 
disk  fan  is  larger  than  is  generally  considered,  and  that  its  de- 
livery is  not  as  much  reduced  by  increasing  the  resistance  under 
which  it  works  as  is  usually  supposed.  The  disk  fan  seems  to  be 
used  much  more  in  Europe  than  it  is  in  America.  Mr.  Wolff 
gives  some  valuable  data  upon  disk  fans  in  Table  III. 

TABLE    III.— QUANTITY   OF   AIR   MOVED    BY   APPROVED    FORMS    OF 
EXHAUST  FAN  DISCHARGING  DIRECTLY  INTO  AT- 
MOSPHERE.    (ALFRED  R.   WOLFF.) 

Cubic  ft. 
per  minute. 
5,000 
8,000 
12,000 
20,000 
28,000 
35,000 
50,000 
80,000 

In  an  article  in  the  "Transactions"  of  the  American  Society 
of  Heating  &  Ventilating  Engineers,  1899  (See  Vol.  V,  p.  128;, 
Prof.  J.  H.  Kinealy  gives  the  following  formula  for  disk  fans  with, 
straight  vanes  set  at  an  angle  of  40  or  45  degrees: 

Q  =  d3  n  -h  3,050, 

where  d  is  the  diameter  in  inches;  n,  the  revolutions  per  minute;, 
and  Q,  the  number  of  cubic  feet  per  minute.     He  also  gives  for 
the  Blackman  fan  (which  has  a  blade  constructed  with  a  peculiar 
curve) : 

Q  =  d3  n  -r-  1,880. 

Prof.  Kinealy  states  that  the  proper  velocity  for  a  fan  is  given  by 
the  formula 

n  =  21,000  -a-  d, 

where  d  is  again  the  diameter  in  inches.  The  formula  is  based! 
on  a  velocity  at  the  rim  of  90  feet  per  second.  Prof.  KinealyV. 
formula  for  the  Blackman  fan  corresponds  quite  closely  with  the> 
figures  given  in  Mr.  Wolff's  table,  and  may  undoubtedly  be  ac- 
cepted as  reliable  for  free  delivery.  If  the  disk  fan  is  used  on  a 
complicated  system  of  ducts  the  author  would  favor  multiplying 
Prof.  Kinealy's  formulas  by  a  coefficient  of  0.65;  and  if  heating 


130  STEAM  HEATING  AND  VENTILATION. 

coils  and  other  similar  resistances  are  added,  this  coefficient  should 
be  made  not  greater  than  0.5. 

Ventilation  ~by  gravity. — There  is  one  method  of  creating  a  cir- 
culation of  air  which  may  properly  be  discussed  in  connection 
with  other  apparatus  for  the  purpose,  and  which  is  frequently 
of  great  value.  This  is  the  heated  flue.  In  Chapter  IV  the  au- 
thor discussed  the  effect  produced  by  heating  the  column  of  air 
in  an  open  flue,  and  the  formula 


was  derived  for  the  theoretical  velocity  in  feet  per  second  (with- 
out friction)  obtained  in  the  flue,  where  T  is  the  temperature  to 
which  the  air  in  the  duct  is  heated,  and  t  is  external  temperature, 
H  being  the  height  of  the  flue,  and  g  the  acceleration  of  gravity 
=  32.2. 

Mr.  Alfred  R.  "Wolff  is  of  the  opinion  that  50  per  cent,  must 
be  deducted  from  the  formula  for  friction  of  air  in  ducts,  etc.,  in 
order  to  get  the  actual  velocity  that  can  be  attained,  and  he  re- 
duces the  formula  to  the  following*  form : 


V  = 


(T  -  t) 

492 


in  which  V  is  the  velocity  in  feet  per  minute.    Mr.  Wolff  also  gives 
the  following  table  calculated  from  this  formula : 

TABLE  IV.— VELOCITY  OF  AIR,  IN  FEET  PER  MINUTE,  THROUGH  A 

VENTILATING    DUCT    (THE    EXTERNAL    TEMPERATURE 

OF  THE  AIR  BEING  32  DEGREES  FAHR. 

Excess  of  Temperature  of  Air  in  Vent  Duct  Above 


Height  of  Vent- 
Duct  in  ft.        5 
10  77 

that  of  External  Air, 
10   15   20   25 
108   133   153   171 
133   162   188   210 
153   188   217   242 
171   210   242   271 
188   230   265   297 
203   248   286   320 
217   265   306   342 
230   282   325   363 
242   297   342   383 

Degrees  Fahr. 
30   50   100 
188   242   342 
230   297   419 
265   342   484 
297   383   541 
325   419   593 
351   453   640 
375   484   656 
398   514   726 
419   541   766 

150 
419 
514 
593 
663 
726 
784 
838 
889 
937 

15  

94 

20  

108 

25  

121 

30  

133 

35  

143 

40  

153 

45  

162 

50.. 

171 

It  will  be  seen  from  this  table  that  the  velocities  obtained  are 
small,  and  as  V  is  proportional  to  the  square  root  of  (T  —  t)  and 
also  to  the  square  root  of  H,  it  is  necessary  to  multiply  one  of 
these  factors  by  four  in  order  to  double  the  velocity.  It  is,  there- 


STEAM  HEATING  AND  TENTILATiON. 


131 


fore,  necessary  to  have  a  very  considerable  difference  in  tempera- 
ture, or  a  great  height  of  flue,  or  a  large  area,  in  order  to  produce 
the  volume  of  flow  that  would  be  required  in  a  moderate  ventil- 
ating plant.  The  cost  of  heating  a  large  volume  of  air  to  the 
required  temperature  is  excessive  in  comparison  with  the  cost  of 
fan  power. 

There  are  many  special  cases,  such  as  the  ventilation  of  the 
toilet  rooms,  where  continual  circulation  is  desired,  and  especially 
where  cheap  gas  is  available,  in  which  the  heated  flue  is  a  valuable 
means  to  be  employed.  In  many  cases  a  vent  shaft  can  convenient- 
ly be  located  around  a  metal  chimney,  from  which  sufficient  heat 
is  obtained  to  produce  a  decided  draft. 


Figure  76.— A  Type  of  Heating  Coil. 


Heating  coils. — In  the  latitudes  of  most  of  the  United  States 
it  is  necessary  to  provide  heating  coils  for  all  fans  which  take  air 
from  the  outside  and  blow  it  into  buildings  for  ventilating  pur- 
poses. These  coils  are  of  many  kinds  and  forms.  They  are  usually 
located  either  between  the  air  intake  and  the  fan,  or  just  at  the 
outlet  of  the  fan,  but  frequently  separate  coils  are  placed  at  the 
base  of  the  vertical  flues  to  each  room;  and  often,  indeed,  a  tem- 
porary coil  for  use  in  very  cold  weather  is  placed  at  the  fan  and 
additional  ones  at  the  separate  vertical  flues.  Figure  76  shows  one 
form  of  heating  coil  for  a  fan,  the  casing  being  removed.  Figures 


132  STEAM  HEATING  AND  VENTILATION. 

77  and  78  show  fan  and  coil  together,  in  the  former  the  heater 
being  on  the  suction  side,  and  in  the  latter  on  the  blast  side. 

The  heating  coils  are  generally  made  of  loops  of  1-inch  pipe, 
and  the  rules  for  proportioning  them  are  very  conflicting.  The 
same  general  theories  apply  to  them  as  to  indirect  radiators,  as 
given  in  a  preceding  chapter  of  this  series. 

In  a  brief  article  in  the  issue  of  May  13,  1899,  The  Engineering 
Eecord  gives  some  valuable  data  from  the  authorship  of  Mr.  W.  S. 
Blessed  of  the  American  Blower  Company.  The  data  refers  to> 
coils  similar  to  that  shown  in  Figure  76,  each  section  of  which  con- 
tains four  rows  of  1-inch  pipes  set  2f  inches  center  to  center,  and 
give  the  final  temperature  attained  by  the  air  under  different 
"mean  velocities"  through  the  coil.  With  air  at  an  initial  "tem- 
perature of  30  degrees  Fahr.  passing  through  the  coils  at  a  mean 
velocity  of  1,600  feet  per  minute,  a  common  velocity  with  a  cen- 
trifugal fan,  the  air  will  be  raised  to  the  temperature  shown  in 
the  following  table,  with  the  steam  pressures  and  number  of  coils, 
in  use  as  mentioned : 

Steam,  5  Ibs.  Pressure.  Steam,  75  Ibs.  Pressure. 

Final  Temp.  Final  Temp. 

Number               of  Air.  Number               of  Air. 

of  Sections.        Deg.  Fahr.  of  Sections.        Deg.  Fahr. 

4  74  4           92 

5  88  5          117 

6  100          6          137 

7  110          7          143 

8  117          8          156 

"With  a  mean  velocity  of  air  of  900  feet  per  minute  the  rise  in 
temperature  of  the  air  will  be : 

Steam,  5  Ibs.  Pressure.  Steam,  75  Ibs.  Pressure. 

Final  Temp.  Final  Temp. 

Number               of  Air.  Number               of  Air. 

of  Sections.        Deg.  Fahr.  of  Sections.        Deg.  Fahr. 

4  85  4          125 

5  110  5  158 

6  130  6  186 

7  147  7  210 

8  160  8  230  \  , 

"With  5  pounds  pressure  about  1,720  B.  T.  U.  are  given  off  per 
hour  per  square  foot  of  heating  surface,  and  with  70  pounds  press- 
ure about  2,520  B.  T.  U." 

Commenting  further  on  this  subject,  in  response  to  an  inquiry, 
The  Engineering  Eecord  of  June  3,  1899,  says: 

"It  may  be  well  to  describe  how  the  manufacturers  of  this  ap- 


STEAM  HEATING  AND  VENTILATION. 


133 


paratus  usually  determine  the  size  of  hot-blast  coils  necessary  to 
do  a  certain  amount  of  work.  It  is  manifest  that  the  amount  of 
heat  which  can  be  transferred  from  one  substance  to  another,  as 
from  the  steam-heated  pipes  of  a  hot-blast  coil  to  the  air  which 
is  being  blown  past  them,  is  proportional,  in  a  measure,  to  the  time 
that  the  air  is  subject  to  the  heating  influence  of  the  steam  pipes. 
Consequently,  hot-blast  coils  must  be  large  enough  in  a  plane 
perpendicular  to  the  direction  of  the  moving  air;  or,  in  other  words, 


Figure  77. — Heater  on  Suction  Side. 

Exhaust. ',      i  Live  Steam 


Figure  78.— Heater  on  Blast  Side. 

they  must  be  a  sufficient  number  of  pipes  wide,  and  the  pipes  must 
be  of  such  a  length  that  the  combined  area  of  the  openings  be- 
tween the  pipes  will  be  sufficient  in  size  to  insure  the  proper  veloc- 
ity of  the  air  to  be  forced  through  them. 

"For  instance,  if  the  mean  velocity  of  air  through  the  coils  is  to 
be  1,600  feet  per  minute,  which  is  not  an  uncommon  one  with  cen- 
trifugal blowers,  and  it  is  desired  to  put  16,000  cubic  feet  of  air 
j)er  minute  through  the  coils,  the  area  of  the  openings  between  the 


134 


STEAM  HEATING  AND  VENTILATION. 


pipes  should  be  16,000  -4-  1,600  =  10  square  feet.  Makers  of  hot- 
blast  coils  know  the  area  of  the  openings  between  the  pipes  of 
coils  of  various  sizes,  and  select  the  size  which  will  give  them  the 
clear  opening  needed.  With  the  data  given  in  the  note  referred 
to,  it  is  possible  to  calculate  the  rise  in  temperature  of  the  air 
which  will  occur  with  various  rows  of  pipes  and  with  steam  of  5 
and  75  pounds  pressure. 

"The  mean  velocity  of  air  should  be  explained.  If  16,000  cubic 
feet  of  air  at  a  temperature  of  say  120  degrees  are  to  pass  through 
the  registers  of  a  ventilating  plant  in  a  minute,  this  air,  when  at 
zero  degrees,  will  have  a  volume  of  about  12,800  cubic  feet.  Con- 
sequently, as  the  air  expands  as  it  is  heated  in  passing  through  the 


200 
190 
.180 


>I50 
1 130 

"°!oo 

I  90 

O    Of) 

tn  80 
70 
60 
50 


100     300     500     700    900    1100     BOO    1500     1700 


Velocity  of  Air  passing  over  Heater  Coils 

Figure  79.— Influence  of  Velocity  of  Air  in  Heaters. 

coils,  its  velocity  must  increase,  and  its  mean  velocity  is  the  one 
upon  which  most  calculations  are  based.  If  the  12,800  cubic 
feet  is  expanded  to  16,000  cubic  feet  its  mean  volume  is  (12,800 
+  16,000)  -f-  2  =  14,400  cubic  feet.  Then  14,400  ~  1,600  (the 
mean  velocity  assumed)  =  9  square  feet,  the  area  of  the  clear 
opening  between  the  coils  that  would  be  needed." 

Mr.  Walter  B.  Snow,  of  the  B.  F.  Sturtevant  Company,  in  a 
lecture  delivered  before  various  technical  colleges,  gives  some  dia- 
grams which,  taken  in  connection  with  the  data  given  above,  are 
of  great  value  in  proportioning  heatinsr  coils.  These  diagrams 
give  only  the  relative  effects  of  varvinor  velocities  through  the  free 
area  of  the  coils,  as  well  as  the  relative  effect  of  different  depths. 
of  coils.  The  diagrams  are  given  in  Figures  79  and  80,  and  aa 


STEAM  HEATING  AND  VENTILATION. 


135 


quoted  from  The  Engineering  Record  of  April  21,  1900,  Mr,  Snow 
gives  the  following  explanation: 

"The  effect  of  varying  velocities*  and  of  different  steam  press- 
ures is  shown  in  the  accompanying  curves  drawn  from  the  results 
of  tests  of  Sturtevant  heaters  used  in  connection  with  fans.  The 
relative  condensation  increases  with  both  of  these  factors,  but, 
as  indicated  by  the  third  curve,  the  relative  temperature  increment 
with  a  given  steam  pressure  decreases  with  the  velocity.  This  is 
the  natural  result  of  moving  a  larger  volume  of  air  across  the 
heating  surface,  and  decreasing  the  time  of  contact.  Disregard- 
ing the  expansion  by  heat,  the  volume  is  proportional  to  the  ve- 


150 

140 
•§130 
#120 


60 


> 
I  50 


2        <o       10       14       18      22       26      30      34      58 
Depth  of  Heater  -  Rows 

Mt  Cftcmtoww  *tOO*fr 

Figure  80. — Influence  of  Depth  in  Heaters. 

locity;  therefore  the  relative  heat  transmission  may  be  determined 
by  multiplying  the  given  velocity  by  the  relative  condensation. 

"The  rate  of  condensation  is  naturally  dependent  upon  the  tem- 
perature difference  "between  the  air  and  steam,  anc*  is  therefore 
greatest  with  the  maximum  difference.  Hence,  the  less  the  depth 
of  the  heater,  the  less  the  total  temperature  increment  of  the  air, 
but  the  more  rapid  the  rate  of  transmission  from  steam  to  air. 
With  increasing  depth  of  heater  there  is  a  corresponding  decrease 
in  the  average  condensation  per  square  foot.  The  surface  first 
exposed  to  the  air,  of  course,  continues  to  maintain  the  same 
efficiency,  but  the  surfaces  subsequently  passed  over  are  progres- 
sively exposed  to  smaller  and  smaller  temperature  differences. 

"The  exact  conditions  in  a  Sturtevant  heater  operated  in  con- 


OFTME 


136  STEAM  HEATING  AND  VENTILATION. 

nection  with  a  fan  which  produces  a  mean  air-velocity  flow  of 
1,200  feet  per  minute  through  the  free  area  of  the  "heater,  are 
presented  in  the  accompanying  curves.  From  these  and  the  pre- 
ceding curves  it  is  evident  that  the  greatest  surface  efficiency  is 
secured  with  the  highest  velocity  of  air  and  the  least  depth  of 
heater.  Practically,  however,  it  is  necessary  to  limit  the  velocity 
of  the  air,  and  to  make  the  heater  of  sufficient  depth  to  give  the 
required  temperature  increment  to  the  air." 

Heating  coils  should  always  be  provided  with  a  by-pass  around 
the  coil,  with  a  damper  that  can  be  opened  in  warm  weather,  when 
the  heating  coil  is  not  in  use;  and  also  in  moderate  weather,  to 
regulate  the  temperature  of  the  entering  air. 

Heating  coils,  although  an  absolute  necessity,  in  almost  every 
case  form  a  resistance  to  the  movement  of  air  which  invariably 
reduces  the  output  of  the  fan ;  and  few,  even  among  those  familiar 
with  ventilating  plants,  realize  the  full 'extent  of  the  resistance 
offered  by  such  coils.  The  author,  in  a  paper  in  the  "Transac- 
tions" of  the  American  Society  of  Heating  &  Ventilating  Engi- 
neers, for  1899  (Vol.  V,  p.  117),  presented  some  tests  made  on 
g'ome  large  fans  in  the  Chicago  Public  Library.  In  the  accom- 
panying tables,  V  and  VI,  are  given  the  principal  results  of  the 
tests: 

TABLE  V.— Test  of  Fan  E.  Diam.  wheel,  78  inches;  width  of  blade,  45  inches; 
diam.  inlet,  54  inches;  net  area,  13.1  sq.  ft.  Main  duct,  45x45  inches;  area, 
14.1  sq.  ft.  Gross  area  heating  coil,  34.7  sq.  ft. ;  surface,  7,200  sq.  ft. 

a*  Pressure  of  Air          Velocity  of  Air.         £  "cs       ft^ 

in  oz.  per  sq.  in.  Ft.  per  min.  ft  M       S  z 

*-l  flj      .      O>    O 


m 


a>S   "'J3 

O  o      •  *» 


g  Q  a>  o. 

ll  I       I       -I          I        dl       *§  I- 

PH  w  «  H  £  gU  fc         < 


By-pass  Open. 


102 

110          .144 

137 

152          .259 

157 


.086 

.173 

1,230 

.... 



6.2 

65 

.086 

.230  • 

1,430 

1,330 

18,700 

8.6 

65 

.115 

.302 

1,700 

1,580 

22,300 

13 

65 

.144 

.403 

1,870 

1,740 

24,500 

17.3 

65 

.144 

.403 

1,920 

1,780 

25,100 

20.6 

65 

By-pass  Closed. 


77 

.151 

.029 

.180 

621 

580 

8,180 

2.9 

65 

77 

.165 

.007 

.172 

650 

605 

9,500 

3 

130 

77 

+.180 

—.015 

.165 

690 

640 

9,010 

'2.9 

160 

144 

.072 

.310 

1,120 

1,040 

14,650 

12 

65 

164 

.334 

.086 

.420 

1,420 

1,320 

18,670 

19.2 

65 

STEAM  HEATING  AND  VENTILATION. 

TABLE  VI.—  Test  of  Fan  F.    Diam.  wheel,  78  inches;  width  blades,  45 
diam.  inlet,  54  inches;  net  area,  13.1  sq.     ft.     Main  duct,   45x45  inches 
14.1  sq.  ft.    Gross  area  heating  coil,  40  sq.  ft.;  surface,  7,200  sq.  ft. 

pj                       Pressure  of  Air         Velocity  of  Air.              £ 
in  oz.  per  sq.  in.             Ft.  per  min.                 a 

fe                                                                                   «              •§ 

Aa         §                      •                         a          £d 

Is     f      1  ;     1        i        1       di 

«                 £               S              H                   ~                  3                0 

137 

inches.; 
;  area, 

<3  -*j 

1° 

By-pass  Open. 

(No  steam  on  coil.) 

73 

.040 

.026 

.065 

788 

730 

10,320 

.  .  . 

86 

.054 

.032 

.086 

945 

830 

12,380 

3.36 

100 

.068 

.040 

.108 

1,"Q3 

1,020 

14,320 

5.16 

114 

.123 

.053 

.176 

1,240 

1,150 

16,250 

7.11 

123 

... 

.061 

I,o50 

1,255 

17,680 

8.88 

139 

... 

.075 

1,520 

1,415 

19,900 

12.1 

143 

... 

.075 

... 

1,580 

1,470 

20,650 

13.5 

By-pass 

Closed. 

(No  steam 

on  coil.) 

76 

.071 

,      .011 

.072 

554 



7,260 

3.05 

141 

.043 

.257 

1,075 

.... 

14,080 

11. 

A  comparison  is  also  given  between  the  air  deliveries  and  power 
required'f  or  both  open  and  closed  by-pass  in  Table  VII.  It  should 
l)e  noted  here  that  the  values  in  columns  (2),  (3),  (5)  and  (6)  were 
obtained  from  Tables  V  and  VI,  but  in  some  cases  by  interpola- 

TABLE  VII.— EFFECT  ON  AIR  DELIVERY  AND   POWER   OF  CLOSING 

BY-PASS. 


(1) 

(2) 

(3) 

(4) 

(5) 

(6) 

(7)          (8) 

(9) 

(10) 

•* 

02 

1 

y  -t 

1 

i 

f-4                             £-t           **         * 

"  03 

d 

fl!| 

.a1* 

5 

Pi 

g 

p,           ^co  § 

§  a, 

'§ 

A 

• 

a 

w 

'*"'  g< 

'"'do? 

m 

fs 

C-2 

C<1 

-1 

o 

^  o 

S        g5g 

00 

g  °  - 

"c3     pi 

to 

^"^     • 

fl    02 

0     02 

V—  'jj         t*          o. 

1 

•4       '        Q 

•  JH 

% 

•[•  fl 

C^    02 

•|>  d        ®  i—5    i 

.j. 

^>    ^ 

O!«M 

^  £  o 

.    CO 

•3  P. 

a» 

h   p, 

£    Pi 

OJ          ^  GJ    >> 

^s    a  >  B 

fa  •Q'w 

<3 

>  ' 

> 

$3 

O 

o 

^     <5 

2-     • 

Fan 

E. 

77 

935 

621 

66.3 

3.2 

2.9 

91. 

... 

65 

77 

935 

650 

69.5 

3.2 

3.0 

94. 

... 

130 

77 

935 

690 

74.0 

3.2 

2.9 

91. 

160 

144 

1,800 

1,120 

64.0 

15.5 

12.0 

77.5        4.9 

2.44 

70 

164 

2,050 

1,420 

69.1 

23.8 

19.2 

80.6        8.4 

2.3 

70 

Fan' 

F. 

76 

850 

554 

65.1 

2.9 

141 

1,550 

1,075 

69.0 

12.5 

11.0 

88.0        4.7 

2.35 

70 

tion,  so  as  to  obtain  for  comparison  the  values  corresponding  to 
the  same  number  of  revolutions  per  minute  of  the  fan  for  open 
and  closed  by-pass. 


138 


STEAM  HEATING  AND  VENTILATION. 


STEAM  HEATING  AND  VENTILATION. 


13$ 


The  following  comments  on  the  results  of  these  tests  were  made, 
and  they  have  a  valuable  bearing  on  practical  installations : 

"It  will  be  seen  that  the  air  delivery  was  decreased  from  21 


Scale 
o/  i'  r  ?'  * 


Figure  82.— Elevations  of  the  Hot-Blast  Unit. 


to  36  per  cent,  merely  by  closing  the  by-pass.  Two  tests  on  fan 
E,  with  part  of  the  heater  turned  on,  and  a  high  temperature 
through  the  fan,  gave  a  somewhat  less  reduction.  But  even  with 
the  by-pass  closed,  and  as  high  a  temperature  as  160  degrees,  the 


140  STEAM  HEATING  AND  VENTILATION. 

delivery  was  20  per  cent,  less  than  with  the  by-pass  open.  The 
only  tests  at  these  high  temperatures  were  made  with  very  low 
fan  speeds,  and  the  test  of  160  degrees  showed  a  negative  pressure 
on  the  blast  side  of  the  fan,  due  to  the  draft  of  the  hot  air  in  the 
vertical  ducts.  The  author  regrets  that  it  was  impossible  to  repeat 
these  temperature  tests  at  higher  fan  speeds,  but  they  do  not  have 
much  bearing  on  practical  results,  as  temperature  in  air  ducts  of 
much  over  100  degrees  would  not  be  good  practice  anywhere.  It 
will  be  noted  also  that  whereas  the  delivery  of  air  is  reduced  about 
24  per  cent,  by  closing  the  by-pass,  the  power  required  (for  same 
speed  of  fan)  is  reduced  only  from  9  to  22  per  cent.,  while  it  will 
be  seen  that  for  equal  air  deliveries  the  power  was  increased  from 
2.3  to  2.44  times  by  closing  the  by-pass. 

"Attention  should  also  be  called  at  this  point  to  the  fact,  as 
shown  by  the  pressure  observations  in  Tables  V  and  VI,  that  even 
with  the  by-pass  wide  open  the  resistance  due  to  intake  and  pas- 
sages through  and  around  the  heater — or,  in  other  words,  the 
total  resistance  on  the  inlet  of  the  fans — was  in  all  cases  quite 
•considerably  more  than  the  total  resistance  of  the  delivery  ducts, 
dampers  and  registers.  This  was  a  matter  of  considerable  sur- 
prise, as  the  intake  seemed  to  be  of  ample  size,  and  area  of  the 
by-pass  large.  It  was  probably  due,  however,  to  the  height  of 
intake  [about  40  feet],  and  as  such  resistances  are  very  often  but 
little  considered,  it  will  be  valuable  to  note  their  importance  in 
this  case." 

In  regard  to  the  fan  capacities  obtained  by  these  tests  it  will 
be  interesting  to  note  that  those  on  fan  E,  with  by-pass  open,  cor- 
respond very  closely  with  those  given  by  Mr.  Huyett's  table,  and 
also  correspond  with  Prof.  Carpenter's  formula  (Q  =  end3)  using  a 
•coefficient  c  =  0.57,  while  with  by-pass  closed  the  coefficient  for 
Prof.  Carpenter's  formula  is  c  =  0.43.  The  velocities  in  the  de- 
livery duct,  however,  even  the  highest  attained,  were  rather  low, 
the  maximum  being  about  30  feet  per  second  (1,780  per  minute), 
which  would  indicate  a  very  free  delivery. 

Arrangement  of  heating  coils  in  air  ducts. — The  possible  arrange- 
ments of  heating  coils  in  ducts  are  limitless,  but  thoroughly  sat- 
isfactory ones,  which  operate  with  perfect  success  in  all  kinds  of 
weather,  are  by  no  means  easy  to  obtain.  Figure  81  shows  the 
arrangement  of  air  ducts,  fan  and  heating  coils  adopted  for  a 
schoolhouse  in  a  large  city,  and  Figures  82  and  83  show  a  detail 


STEAM  HEATING  AND  VENTILATION. 


141 


of  the  arrangement  of  fan  and  heaters.  It  will  be  seen  that  there 
is  a  separate  duct  for  each  room  in  the  building,  each  emanating 
from  the  central  distributing  point,  and  each  provided  with  a 
mixing  damper. 


Front  Elevation  of  Heater 
Showing  SteamGonnections. 


ciHNO  RECORD. 


flush. 


Airim.i 


Fresh  Air  Met.**, 


Figure  83.— Plan  of  One  of  the  Hot-Blast  Units. 


The  system  shown  is  a  good  example  of  a  method  sometimes 
used  to  distribute  air  through  long  ducts  of  small  size.  The 
author  believes,  however,  that  it  is  open  to  criticism,  as  the  large 
number  of  long,  small  ducts  cannot  fail  to  greatly  increase  the 


142 


STEAM  BEATING  AND  VENTILATION. 


frictional  resistance  to  the  flow  of  air,  thus  either  diminishing 
the  fan  capacity  or,  for  a  given  capacity,  greatly  increasing  the 
power  required  to  run  the  fan.  Besides  this,  the  air  in  the  ducts 
opposite  the  center  of  the  fan  will  unquestionably  have  a  higher 
velocity  than  those  at  the  sides.  It  would  have  been  much  bet- 
ter to  locate  centers  of  distribution  convenient  to  the  vertical 
ducts  at  each  end  of  the  building  and  at  each  bicycle  room,  and 


Figure  84, 


Figure  85. 


locate  the  heating  coils  with  mixing  dampers  at  these  points  with 
"feeder"  ducts  (underground,  perhaps)  from  the  fans  to  the  cen- 
ters of  distribution. 

In  this  connection  it  is  well  to  state  that  it  is  not  advisable  to 
run  heated  air  through  underground  ducts,  for  the  reason  that 
they  rapidly  absorb  heat  in  cold  weather.  Where  mixing  dampers 
are  employed,  however,  with  coils  located  at  a  distance  from  the 
fan,  it  is  not  generally  necessary  to  temper  the  air  with  a  coil  at 


STEAM  HEATING  AND  VENTILATION. 


143 


the  fan;  but  all  the  required  heating  surface  can  be  placed  at  the 
•centers  of  distribution. 

Mixing  Dampers. — There  are  innumerable  arrangements  for 
constructing  mixing  dampers,  the  idea  being  to  provide  a  cold-air 
and  a  hot-air  connection  to  the  vertical  flue  to  each  room,,  the 
temperature  of  the  air  to  the  room  being  regulated  by  the  posi- 
tion of  the  mixing  damper.  They  usually  consist  of  a  double 
damper,  one  in  the  cold-air  connection  and  one  in  the  hot-air 
connection,  fastened  together  so  that  when  one  is  entirely  closed 
the  other  is  entirely  open,  and  vice  versa.  Three  types  of  mixing 
dampers,  selected  at  random,  are  shown  in  Figures  84,  85  and  86. 

Thermostats. — Mixing  dampers  are  frequently  arranged  to  be 
operated  by  automatic  thermostats,  which  regulate  their  position 


Room. 


Figure  86. 


by  the  temperature  of  the  room  being  heated.  The  principal  diffi- 
culty is  that  they  frequently  throw  the  dampers  to  the  extreme 
"cold-air  position"  when  the  temperature  rises,  and  to  the  extreme 
"hot-air  position"  when  it  falls  again.  It  is  very  difficult  to  obtain 
a  thermostat  which  will  move  a  mixing  damper  gradually  through 
its  arc  by  means  of  a  small  range  of  temperature  at  the  thermo- 
stat, and  this  is  the  most  important  requirement. 

Air  purification.- — There  is  much  auxiliary  apparatus  employed 
in  ventilating  systems  besides  the  heating  coils,  and  among  these 
may  be  mentioned  especially  means  for  cleaning  and  purifying  the 
air.  In  our  large  cities,  especially  for  hospitals,  something  of  this 
kind  is  very  essential.  The  air  is  frequently  blown  through  loose 
cloth  screens.  The  most  effective  way  of  cleaning  the  air,  how- 
ever, is  to  blow  it  through  a  spray  of  water  or  through  wire  screens 


144 


STEAM  HEATING  AND  VENTILATION. 


over  which  water  is  kept  running,  or  over  shallow  trays  of  water. 
Care  must  be  taken  to  provide  against  the  annoyance  due  to  freez- 
ing, and  the  formation  of  icicles  in  winter.  In  summer  the  water 
will  lower  the  temperature  of  the  air  somewhat,,  but  the  danger 
from  the  washing  process  lies  in  making  the  air  too  damp. 

Mr.  K.  H.  Thomas,  of  Chicago,  a  ventilating  contractor  of  wide 


THE  ENGINEERING  I 

Figure  87.— Plan  of  Air- Washing  Apparatus. 

experience,  has  recently  patented  a  dirt  "eliminator,"  represented 
in  the  accompanying  cuts,  Figures  87  and  88,  which  has  proved 
very  effective  in  severa,  -^e  ventilating  plants.  The  air  is  blown 
through  a  special  form  o  .pray  and  the  eliminator  proper  collects 
the  dirt  and  removes  the  excess  of  moisture  from  the  air. 

Air  cooling. — Trays  of  ice  are  sometimes  used,  and  refrigerating 
coils  also,  for  cooling  the  air  in  summer  for  theaters ;  but  this  is  a 


STEAM  HEATING  AND  VENTILATION. 


145 


luxury  which  has  not  as  yet  been  employed  to  a  large  extent.  It 
must  always  be  remembered  that  any  apparatus  of  the  kind  de- 
scribed will  add  to  the  resistance  through  which  the  fan  has  to 
force  its  air,  and  will  therefore  lessen  its  capacity,  or  must  be 
made  up  by  increased  speed  and  power. 


Figure  88.— The  Eliminator  of  the  Air-Washing  Apparatus. 

Measuring  air  currents. — Before  closing  a  chapter  on  the  ap- 
paratus of  ventilating  systems  it  seems  necessary  to  say  a  few 
words  about  the  instrument  most  always  used  for  testing  pur- 
poses. It  is  not  the  author's  intention  to  treat  of  the  many 


Figure  89. — The  Anemometer. 

methods  to  be  employed  in  testing  ve*  iting  apparatus  for  dif- 
ferent objects,  but  the  anemometer,  w>.  >-h  is  used  to  measure  air 
velocities,  is  so  generally  employed,  and  so  necessary  in  inspect- 
ing plants,  that  a  brief  description  seems  advisable.  There  are 
many  forms,  but  they  all  consist  of  a  set  of  vanes  attached  to  a 


146  STEAM  HEATING  AND  VENTILATION. 

revolving  shaft  like  a  small  windmill  or  disk  fan  and  a  registering 
device  as  shown  in  Figure  89.  They  are  rarely  accurate,  and 
should  not  be»  used  ^ without  being  calibrated.  This  is  usually  ac- 
complished by  attaching  the  instrument  to  the  end  of  a  stick  about 
8  or  10  feet  long,  and  revolving  in  a  circle  at  different  uni- 
form speeds  in  still  air  and  plotting  a  diagram  showing  the  rela- 
tion between  the  actual  velocities  and  the  reading  of  the  instru- 
ment. This  will  give  data  for  correcting  the  indications  of  the 
instrument  obtained  during  a  test, 


INDEX. 


Adams,  Henry  Boilers 

Form  of  direct-indirect  radiator  Cast-iron, 

setting    t-5          Capacities  of 32 

Air  Types   of 31 

Action   of,   in  radiators.... 18,   20,    56  Brick,    Heat   losses    through.... 62,    64 

Amount  of,  required  for  individ-          Bronzing,     Radiator 46 

uals  under  different  conditions    99  Butler,   W.    F. 

Circulation  Handbook  on  ventilation 7 

Around    radiators 43 

In   rooms    96,  110  Carbonic-acid  gas 

Cooling  of  144  Amount  given  oil  by  individuals    S9 

Flow    of  Relation  of,   to  purity  of  air 97 

In    ducts    , 113  Carpenter,  Prof.  R.  C. 

In  heated  ventilating  flue 130      Centrifugal  fan  capacities 127 

Through   indirect   radiators —    50  Coefficients  of  heat  transmission 

Leakage  into  buildings 60          of  building  substances 62 

Pressures  of,  in  ventilating  sys-  Power  to  drive  centrifugal  fans..  128 

terns   115      Radiator   tests 39 

Purification   of 143       Rule   for   direct   radiation 67 

Purity,   standards   of 97       Rule  for  steam  pipe  sizes 76 

Specific   heat   and    weight   of....    61  Tests  of  effect  of  paint  on  radi- 

Velocities  of  ator     4G 

In   ducts   116  Condensation 

Measurement   of 145      Coefficient  of  radiator 43 

Through  inlets  and  outlets 112  Indirect   radiators 

Volumes    required    for    different  Tests    of 51. 

buildings  and  different  periods  Curves   of,    in 54 

of  occupancy 100  Relative,   in  radiators  at  differ- 

Air  inlets  ent  steam  pressures 45 

Diffusers  for,  Cooley,   Prof.   M.   E. 

Theaters 108  Tests  of  wrought-iron  pipe  coils    45 

Upward   svstem  of  ventilation  106    Cooling,     Air 144 

Indirect   radiators 91 

Proper  arrangement  of J09  Dampers 

Velocities    through 112      Mixing    143 

Air  outlets  Use   of,   in   air   ducts 117 

Proper  location  of 109  Denton  &  Jacobus,   Profs. 

Velocities  through 112      Radiator   tests 43 

Air  valves,  see  Valves.  Tests  of  extension-surface  radi- 

Anchors,    riser 85         ators    45 

Anemometer 145  Desaguliers.  Dr. 

System  of  ventilation 8 

Baldwin,  William  J.  Diffusers 

Heat-transmitting       power       of  For    theaters 108 

building  substances 62      For  U.  S.  Senate  chamber 306 

Rule  for  direct  radiation 63  Drainage  of  pipes 78 

Rule  for  pipe  sizes 72  Ducts 

Tests   of   indirect   radiators El  Arrangement  of 

Tests    of    radiator    condensation  For  indirect  radiator  installa- 

at  different   pressures 45  tions   92 

Billings,  Dr.  John  S.  Schemes    for 117 

T,eakaere  of  air  into  buildings...    CO      Branch 116 

Blessed,   W.   S.  Brick    underground 122 

.tieat  given  off  by  heating  coils  132       Flow   of  air   in .113 


INDEX. 

Layout  of,  in  the  basement  of  a         Hcod,  Charles 

large    building 119       Coefficient  of  heat   transmission 

Materials  tor 121          through    glass 62 

Underground     94   Huyett,  M.  C. 

Expansion  Centrifugal    fan    capacities 125 

Method  of  providing  for,  in  pipes    79 

K£nnSi°n  J°intS -81   Jacobus  &  Denton,  Profs. 

JH.XpOSUre  Rurlintnr     t^etc  At 

Influence  of,  in  determining  ra-             TeStsof   extension-surface  -radl 
diatlon    63,    b5         iators   45 

Blackman  Kinealy,    Prof.    J.    H. 

Capacity    of 129       Capacities  of  disk  fans 129 

Centrifugal  Sizes  of  flues  for  indirect  radia- 

Capacity    of 125         tors   ?1 

Capacities,  of,  compared  by  dif- 
ferent   formulas 140   Mills,  J.  H. 

Description    of 124       Rule  for  direct  radiation 66 

Power   to   drive 127       Rule   for  pipe   sizes 73 

Combined  unit  of  heater  and....  133       System  of  piping 16 

Disk  Tests   of   indirect   radiators 51 

Capacities  of 129   Mills'    system    of   piping 16 

Description    of 125   Monroe,    William    S. 

Tests  of,  with  heating  coils 136       Radiator    tests 40 

Filters   for   air   purification 143       Rule  for  direct  radiation €8 

Flues  Rule  for  pipe  sizes 73 

For    indirect    radiator    installa-  Tests  of  fans  and  heating  coils..  136 

tions   DO   Muffler  tank  in  an  office  building 

Heated,  velocity  in  the 130       power     plant 89 

Several   outlets   from  same 121 

Friction  Paints,  Effect  of,  on  radiation 46 

In  steam  pipes 77    Parkes.    Individual    exhalation    of 

See  under  Ducts,  etc.  carbonic-acid    gas 99 

Paul    vacuum    system    of    steam 

Glass,  Window  heating   28 

Heat  losses  through 62,    64  Pettenkofer,  Individual  exhalation 

Governors,    Pump  of   carbonic-acid   gas 99 

On  closed  and  open  heaters.. 23,    26   Plenum     chambers     in    duct    sys- 

Gray,  Dr.,  Tests  of  indirect  radia-  terns   117 

tors 51    Pressures 

Air,   in  ventilating  systems 115 

Hangers  Heating   at   high 19 

Indirect   radiator  supports 91    Pumps 

Pipe,    expansion 87      Automatic   for   return   water 27 

Heat  Vacuum  29 

Amount  given  off  by  direct  rad-          Pipes 

iators     43      Drainage    of 17 

Amount    given     off    by    indirect  Expansion    of 7& 

radiators 50,    51,    70      Protection    of 86 

Loss  in  buildings 60      Supports    for £6 

Required    for   ventilation 61   Pipe  covering 

Heaters,   Feed-water  Values    of    different    kinds    of...    90 

Location  of,  in  an  office  building          Pipe  sizes 

plant  89      Baldwin's  rule 72 

Open     and     closed     or    pressure  Carpenter  &  Sickles'  rule  for 76 

types    22,    23       For    high-pressure    systems r.5 

Value  of   22       For   vacuum    systems 75 

Heating,   Steam  Mills'   rule   for ' 73 

Earliest  instance 7       Monroe's    rule    for 73 

Exhaust  Radiator  connections 76 

Arrangement    of 21,    23    Pipe  systems 

Considerations    of 19       One-pipe 

Gravity  IS          Arrangement   of  mains   for 78 

High  pressure 19          Overhead    or   Mills' .'..    36 

Vacuum     .-..    28          Simple    type 13 

Heating  coils  Sizes    of    radiator    connections 

Arrangement    in    air    ducts 140  to    76 

Capacity    of 132          With  separate  return  main....    15 

For  use  with  fans 131       Overhead   system 

Influence  of  depth  of 135          Description    of    large 83 

Tests   of,    with    fans 136       Two-pipe 

Velocity   of   air   through 132,  134          Arrangement   of  mains   for —    78 

Hogan,  John  J,  Overh'ead    17 

Coefficient  of  heat  transmission  Simple    type 34 

through    glass... ^ 62          Sizes  of  radiator  connections. .    76 


INDEX. 


Piping 

Arrangement  of  main  in  an  of- 
fice building  power  plant 8? 

Connections  to  feed-water  heat- 
ers    23 

For  indirect  radiator  installa- 
tions    £0 

Heating  coil  connections 131,  141 

Radiant  heat,  amount  of,  from  va- 
rious  types   of    radiators 38 

Radiation 
Boiler      capacity     for     required 

amount     of 32 

Calculation    of 85 

Direct 

Adaptation  of 10 

Baldwin's  rule  for C3 

Carpenter's  rule  for 67 

Mills'   rule   for 66 

Monroe's    rule    for 68 

Willett's   rule   for 66 

Wolff's   rule   for 69 

Direct-indirect 

Adaptation  of 11 

Rule    for 71 

Indirect 

Adaptation    of 10 

Rule    for 70 

Raaiant  heat  from 38 

Radiators 

Action    of 36 

Air  circulation  in  hot-water  and 

steam   types E6 

Circulation     of 18,  55 

Classification  according  to  sur- 
face    34 

Connections 

One  and  two-pipe 58 

Riser    79 

Sizes  of 76 

Direct,  circulation  in , 57 

Direct-indirect 

Action    of.. 54 

Settings,   type  of 94 

Types  of  35 

Extension-surface,   tests   of 45 

Flue 

Compared  with  open 45 

Types  of 33 

Gold's    pin 58 

Hot-water 

Compared  with  steam 45 

Types    of 34,  37 

Indirect 

Circulation    in 58 

Heating  residences  by 92 

Theory  of 48 

Types   of 36 

Location  of 46 

Measuring 34 

Narrow  and  wide  compared  with 

high  and  low.....' 44,  45 

One,  two  and  three-column  types  32 

Painting  of 46 

Protection   of  connections  to 86 

Tests   of 38 

Water  in 79 

Wrought-imn    33 

Reed,  J.  R.    Tests  of  indirect  rad- 
iators       51 

Registers 

Velocity  of  air  through 116 

Return   mains.    Location   of 78 

Richards.  C.  B.     Tests  of  indirect 

radiators  51 


Risers 

Anchors   for 85 

Concealment  in  columns 81 

Connections  of,   to  mains 78 

Location    of 83 


Sickles,    E.    C.      Rule    for    steam 

pipe   sizes 76 

Sleeves,   Floor   86 

Snow,  Walter  B. 
Influence    of   velocity    of    air    in 
heaters    and    of    the    depth    of 

heaters   134 

Steam 

Flow    of,    in    pipes 72,    76 

Proportion  of  heat  energy  avail- 
able for  heating 19 

Supports 
Indirect   radiator 91 

Tables 

Air  velocities  at  different  duct 
pressures;  Chap,  ix 115 

Amount  of  air  per  person  in 
buildings  of  various  kinds;  Ta- 
ble 2,  Chap,  vii 101 

Capacity  of  heating  coils;  Chap. 
x  132 

Capacity  of  steam  pipes;  Table 
v,  Chap,  vi 77 

Carbonic-acid  gas  exhalation; 
Chap,  vii 99 

Cast-iron  boiler  capacities; 
Chap.  iii... 32 

Centrifugal  fan-wheel  capacity 
coefficients;  Table  ii,  Chap.  x.  126 

Condensation  in  radiators  at  dif- 
ferent pressures;  Chap,  iii —  45 

Effect  of  by-pass  on  air  deliv- 
ery and  power;  Table  vii,  Chap. 
x  137 

Fan  and  heating-coil  tests;  Ta- 
bles v  and  vi,  Chap,  x 136,  137 

Flue  sizes  for  indirect  radia- 
tors; Chap,  vi 91 

Heat-transmitting  power  of 
building  substances;  Chap,  v  62 

Pipe  sizes  according  to  Baldwin 
and  Mills;  Table  i,  Chap.  vi.  73 

Pipe  sizes,  according  to  Monroe; 
Table  ii,  Chap,  vi 74 

Pipe  sizes,  Webster  vacuum  sys- 
tem; Table  iii,  Chap,  vi 76 

Quantity  of  air  moved  by  ex- 
haust fans;  Table  iii,  Chap,  x  129 

Quantity  of  air  supplied  by 
blowers,  and  power  required  to 
drive;  Table  i,  Chap,  x 127 

Radiator  connections;  Table  iv, 
Chap,  vi 76 

Tests  of  indirect  radiators; 
Chap,  iv 51 

Velocity  of  air  in  heated  flues; 
Table  iv,  Chap,  x 130 

Volume  of  air  necessary  to 
maintain  given  degree  of  pur- 
ity for  different  periods;  Ta- 
ble i,  Chap,  vii 100 

Temperatures 

Air    in    heating-   coils 132 

Tests 

Standards,  in  radiator  tests 43 

(See  under  apparatus  concerned.) 
Thermostats 

Use  with  mixing  dampers 143 


INDEX. 


.56, 


Thomas,  R.  H.  Air  washing  ap- 
paratus    144 

Traps,  automatic,  for  return  wa- 
ter   27 

Tredgold,  Thomas.  Treatise  on 
heating  and  ventilation 7 

Unwin,  Prof.  W.  C.  Flow  of  air 
in  round  pipes 114 

Valves 
Air 

Automatic   

Location    of    radiator. 

Radiators     

Back  pressure 

Forms     of 

Location    of 

For  a  vacuum  system  in  a  Chi- 
cago   office    building 

Location  of,  in  heating  systems. 
Reducing  pressure 

Form    of 

Location    of 

Ventilation 

Air   circulation    in    rooms 

Amount  of  heat  required  for. 61, 

By  gravity 

Early    examples    of   artificial  — 

Need    of    proper 

Plenum  and  exhaust  systems  — 
Upward  versus   downward 


110 


Wall     coils,     Wrought-iron 
Efficiency  of  


pipe, 


-15 


Warner,  W.  Tests  of  indirect  rad- 
iators      51 

Water 

In  radiators 79 

Spray  for  air  purification 143 

Water  line  of  heating  systems..    27 

Webster,  Warren,  &  Co. 
Pipe  sizes  for  vacuum  system..    75 
System  of  steam  heating 28 

Willett,  James  R. 
Capacities  of  cast-iron  boilers...    31 
Rule   for  direct  radiation 66 

Wind 

Influence  of,  on  air  leakage  into 
buildings     60 

Wolff,  Alfred  R. 
Air     velocity     through     indirect 

radiators  50 

Capacities   of   disk   fans 129 

Centrifugal   fan   capacities 125 

Coefficients  of  heat  transmission 

of    building    substances 62,    63 

Form  of  direct-indirect  radiator 

setting    95 

Rule   for  direct   radiation 69 

Velocity   of  air  through  heated 
ventilating  flues 130 

Wood 
Heat  losses  throuerh ....62,    64 

Woodbridge,  Prof.  S.  H. 
Upward   versus  downward  ven- 
tilation    105 

Wren,    Sir   Christopher.     Attempt 
at    ventilation    8 


Ventilation   and   Heating, 

By  JOHN  S.  BILLINGS,  A.  M.,  M.  D., 

LL.D.,  Edinb.  and  Harvard.     D.  C.  L.  Oxon.     Member  of  the 
National  Academy  of  Sciences.      Surgeon,  U.  S.  Army,  etc. 


FROM    THE    PREFACE. 

IN  preparing  this  volume  my  object  has  been  to  produce  a  book  which  will  not  only  be 
useful  to  students  of  architecture  and  engineering,   and   be   convenient  for   reference  by 
those  engaged  in  the  practice  of  these  professions,  but  which  can  also  be  understood  by 
non-professional  men  who  may  be  interested  in  the  important  subjects  of  which  it  treats ; 
and  hence  technical  expressions  have  been  avoided  as  much  as  possible,  and  only  the  sim- 
plest formulae  have  been  employed.     It  includes  all   that   is   practically   important  of   my 
book  on  the  Principles  of  Ventilation  and  Heating,   the  last  edition  of  which  appeared  in 
1889  ;  but  it  is  substantially  a  new  work,  with   numerous   illustrations   of   recent  practice. 
For  many  of  these  I  am  indebted  to  THE  ENGINEERING  RECORD,    in    which    the   descriptions 
first  appeared.  JOHN  S.  BILLINGS. 


TABLE    OF    CONTENTS. 


CHAPTER     I.— Introduction.       Utility     of 

Ventilation. 
CHAPTER    II. — History    and   Literature   of 

Ventilation. 
CHAPTER      III. — The      Atmosphere :       Its 

Chemical  and  Physical  Properties. 
CHAPTER  IV.— Carbonic  Acid. 
CHAPTER     V. — Conditions      Which      Make 

Ventilation      Desirable      or      Necessary. 

Physiology  of  Respiration.     Gaseous  and 

Particulate    Impurities    of    Air.      Sewer 

Air.     Soil    Air.     Dangerous    Gases    and 

Dusts    in    Particular.       Occupations    or 

Processes      of      Manufacture.         Drying 

Rooms. 
CHAPTER  VI. — On  Moisture  in  Air,  and  Its 

Relations  to  Ventilation. 
CHAPTER  VII. — Quantity  of  Air   Required 

for  Ventilation. 
CHAPTER  VIII. — On  the  Forces  Concerned 

in  Ventilation. 
CHAPTER    IX. — Examination    and    Testing 

of  Ventilation. 
CHAPTER  X.— Methods  of  Heating.    Stoves. 

Furnaces.     Fireplaces.      Steam   and  Hot 

Water.     Thermostats. 
CHAPTER     XI. — Sources     of     Air     Supply. 

Filtration  of  Air.     Fresh  Air  Flues  and 

Inlets.     By-passes. " 
CHAPTER  XII.— Foul-Air  or  Upcast  Shafts. 

Cowls.      Svphons. 
CHAPTER  XIII.— Ventilation  of  Mines. 


CHAPTER  XIV. — Ventilation  of  Hospitals 
and  Barracks.  Barrack  Hospitals.  Hos- 

S'.tals  for  Contagious  Diseases.  Blegdam 
ospitals.  U.  S.  Army  Hospitals.  Cam- 
bridge Hospital.  Hazleton  Hospital. 
Barnes  Hospital.  New  York  Hospital. 
Johns  Hopkins  Hospital.  Hamburg  Hos- 
pital. Insane  Asylums.  Barracks. 

CHAPTER  XV.— Ventilation  of  Halls  of 
Audience  and  Assembly  Rooms.  The 
Houses  of  Parliament.  The  U.  S.  Capi- 
tol. The  New  Sorbonne.  The  New  York 
Music  Hall.  The  Lenox  Lyceum. 

CHAPTER  XVI. — Ventilation  of  Theaters. 
Manchester  Theaters.  Grand  Opera 
House  in  Vienna.  Opera  House  at  Frank- 
fort-on-the-Main.  Metropolitan  Opera 
House,  New  York.  Madison  Square 
Theater.  Academy  of  Music,  Baltimore. 
Pu'eblo  Opera  House.  Empire  Theater, 
Philadelphia, 

CHAPTER  XVII.— Ventilation  of  Churches. 
Dr.  Hall's  Church,  New  York.  Hebrew 
Temple,  Keneseth-Israel,  Philadelphia. 

CHAPTER  XVIII. — Ventilation  of  Schools. 
Bridgeport  School.  Jackson  School,  Min- 
neapolis. Garfield  School.  Chicago.  Bryn 
Mawr  School,  near  Philadelphia.  College 
of  Physicians  and  Surgeons,  New  York. 

CHAPTER  XIX.— Ventilation  of  Dwelling 
Houses. 

CHAPTER  XX.— Ventilation  of  Tunnels, 
Railway  Cars,  Ships.  Shops,  Stables. 
Sewers.  Cooling  of  Air.  Conclusion. 


Over  500  Pages.          2JO  Illustrations.  Sent  Postpaid  on  Receipt  of  $4.00. 


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NEW  YORK. 


THE  WAINWRIGHT 


SAFETY  VALVE 


SOFT 

fil/BSf, 


EVEN  FLOW 
FEED  WATER 
HEATER  is 

IN  USE  IN  THE 
LARGEST  POWER 
STATIONS  IN 
THE  COUNTRY, 
ALSO  THE 

WAINWRIGHT 

EXPANSION 

JOINTS. 

Send  for  Catalogue. 


The 

Taunton 

Locomotive 

Manufacturing 

Company, 

Taunton, 
Mass. 


American    Steam   and    Hot- Water 
Heating  Practice* 

From  THE  ENGINEERING  RECORD. 

A  Selected  Reprint  of  Descriptive  Articles,  Questions  and  Answers* 
With  Five  Hundred  and  Eighty-Five  Illustrations* 


PREFACE* 

THE  ENGINEERING  RECORD  (prior  to  1887  THE  SANITARY  EN- 
GINEER) has  for  sixteen  years  made  its  department  of  Steam  and  Hot- 
Water  Heating  and  Ventilation  a  prominent  feature.  Besides  the  weekly 
illustrated  descriptions  of  notable  and  interesting  current  work,  a  great 
variety  of  questions  in  this  field  have  been  answered.  In  1888  Steam- 
Heating  Problems  was  published.  This  was  a  selection  of  questions, 
answers,  and  descriptions  that  had  been  published  during  the  preceding 
nine  years,  and  dealt  mainly  with  steam  heating.  The  present  book  is 
intended  to  supplement  this  former  publication,  and  includes  a  selection 
of  the  descriptions  of  hot-water,  steam-heating  and  ventilating  installa- 
tions in  the  different  classes  of  buildings  in  the  United  States,  prepared 
by  the  staff  of  THE  ENGINEERING  RECORD,  besides  a  collection  of  ques- 
tions and  answers  on  problems  arising  in  this  department  of  building 
engineering,  covering  the  period  since  1888,  in  which  the  heating  of 
dwellings  by  hot  water  has  become  popular  in  the  United  States.  The 
favor  with  which  Steam-Heating  Problems  has  been  received  encourages 
the  hope  that  American  Steam  and  Hot- Water  Heating  Practice  may 
likewise  prove  useful  to  those  who  design,  construct  and  have  charge  of 
ventilating  and  heating  apparatus. 

Size,  8x  JJ  inches*    Three  Hundred  and  Seventeen  Pages*     Price,  $4.00;  postpaid* 


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21  PARK  ROW,  NEW  YORK. 


Pipe  Threading.  .  . 

=  Cutting  Machines 

Combining   in  design  all  tHat  is  latest    and 
best,  and  fully  guaranteed  as  to  construction 


FIG.  I. 


Apex  Nipple  and  Pipe 
Mill  Machine 

IS  SHOWN  BY  FIG.  I. 

The  gearing  is  entirely  protected 
from  dust ;  six  different  speeds  pos- 
sible with  but  a  three-step  cone. 
Pump  is  out  of  way  of  operator  ;  vise 
open  or  closed  while  machine  is  in 
motion.  Nipple  grips  may  be  closed 
on  threaded  ends  of  pipe  without  in- 
jury to  thread,  thus  avoiding  the 
necessity  of  screwing  nipple  into 
grips  after  they  are  closed  ;  this 
feature  possessed  by  no  other  machine. 
With  this  machine  we  furnish  an  au- 
tomatic threading  gauge.  Both  left 
and  right-hand  threads  may  be  made. 
A  description  in  more  detail  will  be 
found  in  our  catalogue. 


Combined  Hand  and  Power  Pipe 
Threading  and  Cutting  Machine 

IS  SHOWN  BY  FIG.  II. 

We  make  this  machine  in  several  sizes.  It  is  so 
arranged  that  either  hand  or  power  may  be  used 
at  will,  and  it  may  be  readily  taken  from  its  base 
and  us3i  as  a  portable  hand  machine.  It  occupies 
less  floor  space  and  guaranteed  to  do  better  work 
than  any  other  combined  machine  on  the  market. 
Equipment  substantially  the  same  as  that  of  our 
portable  machine,  the  description  of  which  follows. 


FIG.  II. 


Our  Portable   Machine 

IS  SHOWN  BY  FIG.  III. 
Made  in  a  number  of  sizes.  In  quality 
of  work  and  rapidity  of  action,  both  in 
threading  and  cutting,  this  machine  is 
far  superior  to  any  other.  The  possible 
range  of  its  work  is  greater,  and  quicker 
changes  from  size  to  size  'are  a  feature. 
We  furnish  with  this  machine  our 
Standard  Adjustable  Quick  Opening 
and  Closing  Die  Head  and  our  improved 
Cutting-off  Knife.  The  chasers  are  set 
by  graduation  to  any  size  desired,  are 
released  from  threading  while  in  motion, 
open  to  permit  the  cutting  of  the  pipe, 
and  closed  instantly  and  positively ; 
readily  replaced  by  other  sizes.  The 
vise  is  self-centering  and  actuated  by 

rack  and  pinion.    Gears  completely  housed  from  dust  and  to  no  part  of  the  machine 

are  chips  accessible,  to  its  detriment. 

We  issue  a  complete  catalogue  fully  describing  and  illustrating  the  various  types 

of  our  machines  and  will  be  glad  to  send  it  on  request. 

THE  HERRELL  flFQ.  CO.,  Toledo,  Ohio. 

European  Office:  The  Fairbanks  Co.,  16  Great  Eastern  St.,  London,  E.  C. 


FIG. 


Water- Works  for  Small  Cities  and  Towns, 

By    JOHN    GOODELL. 


PUBLISHERS'  ANNOUNCEMENT. 

THIS  book  is  a,  description  of  the  methods  of  construction  of  the  various  portions  of 
a  water-works  plant,  outside  of  a  few  features,  like  pumps,  which  are  now  left,  in  a 
large  measure,  to  the  manufacturers  of  standard  specialties.  Even  in  respect  to  these 
specialties  enough  general  information  is  given  to  enable  anyone  with  ordinary  intelligence 
to  understand  the  technical  descriptions  in  manufacturers'  catalogues  and  the  statements 
of  their  agents. 

The  theory  of  the  flow  of  water,  the  strength  of  materials  entering  into  a  water-works 
plant,  of  the  wind  pressure  on  stand-pipes  and  similar  matters  are  mentioned  as  briefly  as 
possible  because  they  are  thoroughly  taught  in  technical  schools  and  explained  in  numerous 
text  books.  On  the  other  hand,  there  is  no  book  giving  a  general  account  of  the  methods 
of  building  and  maintaining  works,  dams,  pipe  lines,  reservoirs,  stand  pipes  and  other  fea- 
tures in  sufficient  detail  to  enable  an  engineering  student  to  understand  properly  the  ap- 
plication of  the  theories  he  learns  in  school. 

There  is  another  class  to  whom  it  is  believed  the  book  will  ba  particularly  valuable, 
and  that  is  superintendents  of  works  and  engineers  who  may  have  occasion  to  require  tho 
compilation  of  the  best  information  of  any  feature  of  such  a  plant.  Even  if  a  superinten- 
dent is  thoroughly  acquainted  with  the  subject  on  which  he  must  prepare  a  report,  it  often 
happens  that  from  lack  of  experience  in  writing  he  may  have  difficulty  in  preparing  it.  In 
such  a  case,  'it  is  confidently  believed,  this  book  will  prove  of  assistance,  particularly  as  it 
has  been  written  very  largely  with  the  idea  of  proving  serviceable  to  men  without  technical 
education  called  upon  to  act  as  members  of  a  water  commission. 

In  view  of  the  fact  that  the  information  presented  has  been  acquired  by  correspondence 
with  water-works  officials  in  many  parts  of  the  country  and  a  review  of  all  the  published 
information  of  value  on  the  subject,  it  is  believed  that  even  engineers  and  water-works 
managers  cf  experience  in  their  specialty  will  find  the  book  of  interest  in  a  number  of  par- 
ticulars. 

TABLE  OF  CONTENTS. 


CHAPTER   I.— SURFACE  WATER— 

The  Yield  of  Catchment  Areas — Gauging 

Stream    Flow — The    Meaning    of    Water 

Analyses. 
CHAPTER   IT. — EARTH  DAMS — 

Clay — -Gravel  —  Masonry  Core  Walls  • — 

Water    in    Earthwork — Cross-section    cf 

the     Embankment — Starting     the     Core 

Wall. 

CHAPTER     ITI. — MINOR      DETAILS      OF 
RESERVOIRS— 

Outlet        Pipes  —  Gate-Houses  —  Waste- 
Weirs. 
CHAPTER   IV.— TIMBER  DAMS— 

Brush      Dams  —  Crib      Dams  —  Framed 

Dams. 
CHAPTER  V.— MASONRY  DAMS— 

Foundations — Materials — Eart h   Backing 
—  Design  —  Specifications  —  Rock-Fill 

Dams. 

CHAPTER   VT.— SPECIAL  FEATURES  OF 
RIVER  AND  POND  SUPPLIES — 

Head-Works — Effect  of  Storage  on  Water 

— Odors  in  Water. 

CHAPTER     VII. — GROUND-WATER     SUP- 
PLIES— 

Methods  of  Collecting  Ground   Water — 

Quantity  of  Ground  Water. 
CHAPTER  VIII. — THE  UTILIZATION  OF 
SPRINGS — 

Springs  in  Plains — Hillside  Springs. 
CRAPTER  IX. — OPEN  WELLS. 
CHAPTER  X. — DRIVEN  WELLS — 

Sinking     Wells  —  Air    in     Wells  —  Well 

Specifications. 


CHAPTER  XI. — DEEP  AND  ARTESIAN 
WELLS— 

Sinking  Wells — Specifications — Yield  of 
Wells — Quality  of  Ground  Water. 

CHAPTER  XII. — PUMPS — 

Steam  Consumption  —  Power  Pumps  — 
Details  of  the  Water  End — Special  Power 
Pumps. 

CHAPTER  XIII.— THE  AIR  LIFT. 

CHAPTER  XIV. — PUMPING  STATIONS. 

CHAPTER  XV.— INTAKES   AND    INTAKE 
PIPES. 

CHAPTER     XVI.— CLARIFICATION     AND 
PURIFICATION  OF  WATER— 
Turbidity — Slow  Sand  Filters — Mechani- 
cal Filters. 

CHAPTER  XVII. — THE  PIPE  SYSTEM— 
Flow  of  Water  in  Pipes — Data  Concern- 
ing   Pipe    and     Accessories — -Submerged 
Pipe — Clay  Pipes  and  Open  Channels. 

CHAPTER  XVIII. — SERVICE  RESER- 
VOIRS AND  STAND  PIPES— 
Concrete-Lined  Reservoirs  —  Asphalt- 
Lined  Reservoirs  —  Stand  Pipes  and 
Water  Towers — Substitutes  for  Stand 
Pipes. 

CHAPTER  XIX.— THE  QUANTITY  OF 
WATER  TO  BE  PROVIDED — 
Relative  Capacities  of  Small  Works  for 
Domestic  Supply  and  Fire  Protection — 
The  Influence  of  Small  Street  Mains- 
Fire  Streams. 

CHAPTER  XX.— THE  WATER  WORKS 
DEPARTMENT— 

Financial  Considerations  —  Checking 
Water — Keeping  up  the  Works. 


Bound  in  Cloth,  8vo. 


28J  Pages. 


Price,  $2.00,  Postpaid. 


THE 

2J  PARK  ROW, 


ENGINEERING    RECORD, 


NEW  YORK. 


-MASON 

Reducing  Valves 

ARE  THE  WORLD'S  STANDARD  VALVES 

For  automatically  reducing  and  absolutely 
maintaining  an  even  steam  or  air  pressure. 

THey  are  adapted  for  every  need  and 
guaranteed  to  -worK  perfectly  in  every 
instance. 

For  Vacuum  Systems  of  Heating  we  maKe 
a  special  valve. 

WRITE  FOR  FULL  INFORMATION  AND 


SPLENDID   REFERENCES. 


THE  MASON  REGULATOR  CO.,  BOST*.  AASS"' 


/T~AHE  best  designed  system  of  heating  and  ventila- 
tion may  be  rendered  almost  worthless  by  the 
use  of  inferior   apparatus — inferior   either   in   design, 
material  or  workmanship. 


Our  design 
represents 
the  most 
advanced 
practice. 


Mechanical 
Draft 
Fans. 


The  circula- 
tion in  this 
coil  is  posi- 
tive, either 
under  vac- 
uum or  100 
.Ifce.  steam 
pressure. 


We  cheerfully  furnish  plans  and  drawings 
to  those  interested. 

Massachusetts  Fan  Company, 


Room  50,  Stock  Exchange  Building,     = 


BOSTON,  MASS. 


American  Plumbing  Practice. 

From  THE  ENGINEERING  RECORD. 

A.  Selected  Reprint  of  Articles  Describing  Notable  Plumbing  Installations 
in  the  United  States,  and  Questions  and  Answers  on  Problems 

Arising  in  Plumbing  and  House  Drainage. 
With  Five  Hundred  and  Thirty-Six  Illustrations. 


PREFACE. 

THE.  ENGINEERING  RECORD,  prior  to  1887  THE  SANITARY  EN- 
GINEER, has  for  17  years  given  much  attention  to  domestic  water  supply, 
house  drainage,  ventilation,  and  plumbing.  Beside  the  frequent  illustrated 
descriptions  of  notable  and  interesting  current  work,  a  great  variety  of 
questions  in  this  field  have  been  answered.  In  1885  "Plumbing  and  House 
Drainage  Problems"  was  published. 

The  present  volume,  " American  Plumbing  Practice,"  is  a  compilation 
of  illustrated  descriptions  of  plumbing  installations  in  modern  buildings 
of  every  character,  together  with  Notes  and  Queries  touching  interesting- 
points  developed  in  practice,  from  articles  which  have  appeared  in  THE 
ENGINEERING  RECORD  since  the  publication  of  "Plumbing  and  House 
Drainage  Problems/'  Within  this  period  the  towering  office  building  has 
been  developed,  involving  special  problems  of  drainage  and  plumbing. 
The  equipment  of  hotels,  hospitals,  amusement  halls,  swimming  baths,  and 
other  public  buildings  has  been  upon  the  most  thorough  and  elaborate 
scale,  and  in  the  description  of  the  plumbing  of  residences  examples  may 
be  found  of  nearly  every  class  of  dwelling.  Its  division  of  Notes  and 
Queries  is  intended  to  supplement  "Plumbing  Problems/7  bringing  these 
queries  well  up  to  date.  The  greater  part  of  the  book  consists  of  descrip- 
tive matter  nowhere  else  available  in  this  permanent  form. 

Sent  Postpaid  on  Receipt  of  $3.00. 


THE    ENGINEERING    RECORD, 

21  PARK  ROW,  NEW  YORK. 


GURNEY   HEATERS 

Are  of  uniform  excellence.  In  all  of  them  the 
heating  surfaces  are  so  arranged  as  to  produce  a 
maximum  of  heat  from  a  minimum  amount  of  coal. 
All  are  made  from  the  best  grades  of  iron,  have  the 
most  efficient  types  of  grates,  and  embody  all  the 
latest  improvements. 

The  "Doric  "and  "400  Series,"  Steam  and  Hot 
Water  Heaters  are  made  for  a  moderate  line  of 
work,  particularly  house  heating  purposes,  and  the 
"BRIGHT  IDEA"  Series  for  the  larger  systems. 
Their  capacities  are  fully  guaranteed. 


SEND  FOR  LATEST  TRADE  CATALOGUE. 

GURNEY    HEATER    flFQ.    CO., 

74   Franklin  St.,   Boston.  Ill    Fifth  Ave.,   New  York. 

Western  Selling  Agents:    JAMES  B.  CLOW  &  SONS,  222-224  Lake  St.,  Chicago,  III. 


ASBESTOS  AND  MAGNESIA  PRODUCTS 

NON-HEAT-CONDUCTING   COVERINGS 
FOR  HEATING  AND  POWER   PLANTS 

Send  for  pamphlet  "SAVE    FUEL. ' ' 

Asbesto,  Sponge  Felted,  Magnesia, 
Asbestos  Fire  Felt. 
Asbestocel  (Air-Cell). 

Sectional  Pipe  and  Boiler  Coverings. 
Keystone  Hair  Insulation— 

Structural   Insulator,    Sound  Deadener,  Cold 
Preserver. 

"Nonburn"  Asbestos  Building  Paper. 
Asbesto-Metallic  Steam  Packings. 

H.    W.    JOHNS-MANVILLE    CO., 

100  WILLIAM  STREET,  NEW  YORK. 


MILWAUKEE.  CHICAGO. 

CLEVELAND 


ST.  LOUIS. 
PITTTSBURGH. 


BOSTON.  PHILADELPHIA. 

NEW  ORLEANS. 


Some    Details    of    Water-Works 
Construction, 


By  W.  R.  BILLINGS. 

Formerly  Superintendent  of  Water-Works  at  Taunton,  Mass. 

With  Illustrations  from  Sketches  by  the  Author* 


AUTHOR'S    INTRODUCTORY    NOTE. 

Some  questions  addressed  to  the  editor  of  THE  ENGINEERING  RECORD  by  persons 
in  the  employ  of  new  water-works  indicated  that  a  short  series  of  practical  articles 
on  the  Details  of  Constructing  a  Water- Works  Plant  would  be  of  value;  and,  at 
the  suggestion  of  the  editor,  the  preparation  of  these  papers  was  undertaken  for 
the  columns  of  that  journal.  The  task  has  been  an  easy  and  agreeable  one,  and  now, 
in  a  more  convenient  form  than  is  afforded  by  the  columns  of  the  paper,  these  notes 
of  actual  experience  are  offered  to  the  water-works  fraternity,  with  the  belief  that 
they  may  be  of  assistance  to  beginners  and  of  some  interest  to  all. 


TABLE    OF    CONTENTS. 


CHAPTER  I.  —  MAIN  PIPES  — 

Materials  —  Cast-Iron  —  Cement-Lined 
Wrought  Iron  —  Salt-Glazed  Clay  —  Thick- 
ness of  Sheet  Metal  —  Methods  of  Lining 

—  List  of  Tools  —  Tool-Box  —  Derrick  — 
Calking  Tools  —  Furnace  —  Transportation 

—  Handling  Pipe  —  Cost  of  Carting  —  Dis- 
tributing Pipe. 

CHAPTER  II.—  FIELD  WORK— 

Engineering  or  None  —  Pipe  Plans  —  Spe- 
cial Pipe  —  Laying  out  a  Line  —  Width 
and  Depth  of  Trench  —  Time-Keeping 
Book  —  Disposition  of  Dirt  —  Tunneling  — 
Sheet  Piling. 

CHAPTER  III.—  TRENCHING  AND   PIPE- 
LAYING— 

Caving  —  Tunneling  —  Bell-Holes  — 
Stony  Trenches  —  Feathers  and  Wedges  — 
Blasting  —  Rocks  and  Water  —  Laying 
Cast-Iron  Pipe  —  Derrick  Gang  —  Hand- 
ling the  Derrick  —  Skids  —  Obstructions 


Pipe  —  Derrick 
g  th 
Left  in  Pipes  —  Laying  Pipe  in  Quicksand 


—  Cutting  Pipe. 


CHAPTER     IV.— P  I  P  E-L  A  Y  I  N  G     AND 
JOINT-MAKING— 

Laying  Cement-Lined  Pipe — "Mud"  Bell 
and  Spigot  —  Yarn  —  Lead  —  Jointers — 
Roll  —  Calking  —  Strength  of  Joints  — 
Quantity  of  Lead. 

CHAPTER  V.— HYDRANTS,  GATES,   AND 
SPECIALS. 

CHAPTER  VI.— SERVICE  PIPES— 

Definition — Materials — Lead  vs.  Wrought 
Iron — Tapping  Mains  for  Services — Dif- 
ferent Joints — Compression  Union — Cup. 

CHAPTER     VII.  —  SERVICE-PIPES     AND 
METERS— 

Wiped  Joints  and  Cup-Joints — The  Law- 
rence Air-Pump — Wire-Drawn  Solder — 
Weight  of  Lear  Service-Pipe — Tapping 
Wrought- Iron  Mains  —  Service- Boxes  — 
Meters. 


Large  8vo.     Cloth,  $2.00,  Postpaid* 


THE    ENGINEERING    RECORD, 


21  PARK  ROW, 


NEW  YORK. 


The  Architect  or  Engineer 

who  fails  to  investigate  claims  to  surpassing  merit 
made  by  any  apparatus  entering  into  his  work, 
constantly  runs  the  risk  of  remaining  ignorant  of 
something  he  would  most  gladly  know  of.  The 

"Webster  System" 

of  Steam  Circulation  for  Heating  Purposes  lays 
claim  to  an  efficiency  and  economy  which,  if 
vindicated,  constitute  that  system  a  class  by  itself. 
If  the  steam  heating  of  a  large  and  important 
building  is  a  problem  you  must  shortly  solve, 
we  shall  be  pleased  to  have  you  write  us. 

\Varren  AVebster  (SL  Co.,  Camden,  N.  J. 

NEW  YORK,  322  Broadway.        PHILADf  LPHIA,  1105  Stephen  Girard  Bldg. 
BOSTON,  743  Fremont  Bldg.       CHICAGO,  1509  Monadnock  Bldg.        ST.  LOUIS,  621  Century  Bidg. 


STEAM  PIPE  AND  BOILER  COVERINGS 

ASBESTOS  GOODS 
TRADE  SUPPLIED  CONTRACTS  EXECUTED 

ROBERT    A.    KEASBEY 

Telephone  is i s  coniandt  83  Warren  Street,  Ne'w  York 

The  "EM-ESS"  SELF-CLOSING  FAUCETS 

having  been  honestly  made  by  us  for  twenty  years, 
were  naturally  reliable,  never  "stuck  open,"  and  de- 
servedly popular.  Hence  the  numerous  imitations 
that  have  appeared.  The  word  "Doherty"  is  now  pub- 
lic property,  and  is  used  simply  to  designate  a  type  of 
self-closing  Faucet  which  is  made  by  so  many  people 
that  the  name  no  longer  affords  a  guarantee  of  dura- 
bility. Plainly  specify  The  "Em-Ess"  Self-C los- 
ing Cocks,  which  are  made  by  us,  exclusively,  and 
look  for  our  stamp. 

The  MEYER=SNIFFEN  CO.,  Ltd., 

CLOSING  5  East  19th  Street,  New  York. 


PHILADELPHIA. 


WESTFIELD,  MASS. 


THE   H.  B.  SMITH   CO. 


133-135     CENTRE     STREET,     N.  Y. 

Manufacturers     of 


The  Mercer  Boiler. 


STEAM  &  WATER 

HEATING 
APPARATUS 

For  all  Kinds  of  Buildings. 
Send  for  Catalogue.     '•'•     •• 

BOILERS.  — Mills,    Mercer,    Gold,    Cottage,    Menlo. 
RADIATORS]  Imperial,  Princess,  Union,  Royal  Union, 

(Direct),     j     Sovereign,  Coronet,  Diadem,  etc. 
RADIATORS  j  Gold's  School  Pins,  R  &  L  Nipple  Pins, 

(Indirect),    j     Drum  Pins,  etc. 


Reliable  News  Regarding  New  Construction. 


THE  ENGINEERING  RECORD 

work  for  which  bids  are  to  be  asked,  likewise  reports  of  bids  submitted — all  care- 
fully edited  in  order  to  eliminate  items  of  no  value  to  a  contractor,  manufacturer  or 
dealer  in  building  and  engineering  supplies. 

It  was  established  in  1877,  and  spends  a  good  deal  of  money  to  secure  and 
print  only  useful  items.  Hence  the  reputation  for  reliability  which  it  has  attained. 

Its  Contracting  news  and  Advertisements  inviting  bids  for  projected  work  from 
the  Government,  State  and  Municipal  authorities,  cover  work  in  all  sections  of  the 
United  States  and  Canada. 

They  relate  to  Water- Works,  Sewers,  Sewage  Disposal,  Bridges,  Public  Build- 
ings, Business  Buildings,  Schools,  Railroad  Depots,  New  Manufactories,  Dwellings 
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Government  Work  and  Miscellaneous  Work — including  contract  prices  as  recorded 
in  bids  submitted. 

Each  issue  contains  important  news  items  not  previously  published  elsewhere. 

It  is  issued  so  as  to  reach  subscribers  within  a  radius  of  400  miles  of  New  York, 
on  Saturday;  within  fifteen  hundred  miles,  on  Monday,  and  the  Pacific  Coast,  on 
Thursday,  of  each  week. 


Hot- Water  Heating  and  Fitting, 

A  Treatise  on  the  Practice  of  Warming:  by  Hot  Water,  with  Modern 
Methods  Described  and  Explained. 


By    WILLIAM    J.    BALDWIN,    M.  E. 


The  book  contains  much  of  the  matter  on  this  subject  which  has  appeared  in  the 
columns  of  THE  ENGINEERING  RECORD,  together  with  a  large  amount  of 
additional  original  data;  the  whole  containing  a  large  amount  of  practical 
and  useful  information  of  great  value  to  the  Engineer,  Architect,  Mechanic, 
and  Householder.  Handsomely  bound  in  cloth  and  fully  illustrated,  392  pp. 
Among  the  questions  treated  are  the  following: 


The  cause  cf  the  circulation  of  the  water 
within  heating  apparatus. 

Motion  explained  by  the  use  of  diagrams. 

liow  to  find  the  velocity  of  .the  flow  of  water 
in  pipes  of  an  apparatus. 

Simple  lormulse  explaining  the  laws  which 
govern  the  flow  of  water  in  an  apparatus. 

Diagrams  showing  the  coefficients  of  the 
curve  of  the  expansion  of  the  water. 

Diagram  showing  the  velocity  of  water  in 
feet  per  second  when  the  height  from 
which  it  flows  is  known. 

The  use  of  the  diagrams  in  estimating  the 
flow  of  the  water  through  the  apparatus. 

Table  of  the  quantity  of  water  in  U.  S.  gal- 
lons that  will  pass  through  pipes  of  a 
given  diameter. 

Table  giving  the  friction  loss  in  inches  of 
the  water  head  for  each  ten  feet  of 
length  of  different  sizes  of  clean  iron 
pipes  discharging  given  quantities  of 
water  per  minute. 

The  loss  of  head  by  friction  and  resistance 
of  elbows. 

Saving  by  long  radius  elbows. 

Saving  by  smooth  elbows. 

Resistance  caused  to  the  flow  of  water  by 
elbows  and  return  bends. 

Resistance  caused  by  valves,  etc.,  and  how 
it  may  be  made  less. 

How  to  find  the  flow  of  water  through  main 
pipes  of  an  apparatus. 

To  find  the  quantity  of  water  in  U.  S.  gal- 
lons that  will  pass  when  the  total  head 
is  known. 

To  find  the  fM^meter  of  a  pipe  for  a  given 
discharge  of  water. 

To  find  the  discharge  of  pipes  for  given 
diameters. 

How  to  compute  radiating  surfaces. 

Experiments  of  Tredgold  and  Hood  in  warm- 
ing surface. 


modern     investigators    on 


Experiments    of 
radiators. 

How  to  find  the  amount  of  water  that 
should  pass  through  a  radiator  to  do 
certain  duty. 

How  to  determine  the  size  of  inlet  and  out- 
let to  hot-water  radiators. 

How  to  estimate  the  quantity  of  water  that 
should  pass  through  a  radiator  for  a  loss 
of  10  degrees. 

Diagram  giving  the  diameter  of  flow  and  re- 
turn pipes  when  the  radiating  surface 
and  the  length  of  the  pipes  are  known. 

Experiments  illustrating  use  of  diagram  in 
the.  piping  of  buildings. 

The  different  systems  of  mains  used  in  hot- 
water  heating. 

Treatment  of  single  circuits. 

Branch  circuits. 

Compound  circuits. 

How  to  proportion  the  apparatus  for  in- 
direct heating. 

Heat  given  off  per  square  foot  of  surface. 

Loss  of  heat  through  walls  and  windows  of 
a  room. 

Heat  lost  by  ventilation— how  to  consider  it. 

How  to  find  heating  surface  of  a  room 
warmed  by  indirect  radiation. 

Comparative  experiments  with  hot-water 
coils. 

Diagram  of  sizes  of  main  pipes  for  indirect 
radiation. 

Examples  of  buildings  warmed  by  hot  water. 

Boilers  used  in  hot- water  apparatus. 

Direct  and  indirect  radiators  used  in  hot- 
water  apparatus. 

Expansion  tanks  and  how  they  should  be  used. 

Special  fittings  for  hot-water  apparatus. 

How  to  conduct  experiments  in  testing  the 
efficiency  of  hot-water  radiators. 

How  to  control  fires  by  the  temperature  of 
water. 


Large  8vo.      392  Pages,  Fully  Illustrated.      Sent  Postpaid  on  Receipt  of  $2.50. 


THE 

21  PARK  ROW, 


ENGINEERING    RECORD, 


NEW  YORK. 


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DUE  AS  STAMPED  BELOW. 

UG  0  I    L'32 

FORM  NO.  DD6                        UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
50M    6-00                                               Berkeley,  California  94720-6000 

